I have decided to compile a list of noteworthy free FPSes. All of the following games are multiplayer only. I know I probably missed some, so please help me add to this list.
All of the games have fairly low system requirements. I have not tried all the listed games, and thus my descriptions may seem a bit lacking.
The screenshot link and the spoiler the image under spoiler tags are the same.
<a href="http://urbanterror.net" target="_blank">Urban Terror</a>riginally a mod of Quake III Arena, UT is now a standalone game. Its gameplay is comparable to Counter-Strike
<a href="http://www.redwoods.net/images/urbanterror_ingame.jpg" target="_blank">Screenshot Link</a>
<a href="http://www.youtube.com/watch?v=0irPKekjzuA" target="_blank">Video</a>
<a href="http://warrock.gamersfirst.com/index.php" target="_blank">War Rock:</a> An FPS akin to Battlefield (or at least in my eyes). Features many vehicles. Free to play, but some items require money.
<a href="http://www.youtube.com/watch?v=bUBdg7pT5Lk" target="_blank">Video Link</a>
<a href="http://www.mmoginfo.com/imagenes/foto_war_rock.jpg" target="_blank">Screenshot</a>
<a href="http://www.gunzonline.com/" target="_blank">Gunz: The Duel</a>: Not exactly an FPS (it's a third person shooter), but I though I'd include it anyway. Non-traditional shooter, but very fun
nontheless. Has some RPG elements as well, like leveling up. I'd recommend you try the north american version, as it has more game modes. Very large user base, with a few thousand on at any given time.
<a href="http://www.youtube.com/watch?v=jV8a0JUlfnw" target="_blank">Video Link</a>
<a href="http://i63.photobucket.com/albums/h146/Odinius/gunz_gross01.jpg" target="_blank">Screenshot</a>
<a href="http://www.joinfear.com/main" target="_blank">F.E.A.R. Combat:</a> This is the multiplayer portion of the commercial FPS Fear.
<a href="http://www.youtube.com/watch?v=HmOhqsbqs6I" target="_blank">Video Link</a>
<a href="http://xubanu.files.wordpress.com/2006/08/fear_big.jpg" target="_blank">Screenshot</a>
<a href="http://www.ijji.com" target="_blank">Soldier Front:</a> Tactical shooter available on ijji website.
<a href="http://www.youtube.com/watch?v=hSsl5gAsJ4g" target="_blank">Video Link</a>
<a href="http://www.gameogre.com/reviewdirectory/upload/Soldier%20Front.jpg" target="_blank">Screenshot</a>
<a href="http://www.nexuiz.com/" target="_blank">Nexuiz:</a> Quake-style shooter. Very fast paced arcade-like shooter.
<a href="http://www.youtube.com/watch?v=4E5kRPp9m3E" target="_blank">Video Link</a>
<a href="http://shazbot.blogsome.com/wp-admin/images/nexuizDNAQualDetails.jpg" target="_blank">Screenshot</a>
<a href="http://www.warsow.net/?page=home" target="_blank">Warsow:</a> Extremely fast-paced FPS with cel-shaded graphics.
<a href="http://www.youtube.com/watch?v=iB72-rCnuwk" target="_blank">Video Link</a>
<a href="http://www.gameogre.com/reviewdirectory/upload/Warsow.jpg" target="_blank">Screen</a>
<a href="http://www.planetwolfenstein.com/features/articles/pw_faq_et.shtml" target="_blank">Wolfenstein: Enemy Territory:</a> War based FPS, highly polished. Fairly large community.
<a href="http://www.youtube.com/watch?v=GIeH7h0HTlk" target="_blank">Video Link</a>
<a href="http://i.d.com.com/i/dl/media/dlimage/59/13/5913_large.jpeg" target="_blank">Screenshot</a>
<a href="http://www.americasarmy.com/" target="_blank">America's Army:</a> Tactical FPS sponsored by the US military.
<a href="http://www.youtube.com/watch?v=Z6SVueaI-cM" target="_blank">Video Link</a>
<a href="http://static.howstuffworks.com/gif/americas-army-3.jpg" target="_blank">Screenshot</a>
<a href="http://doa.cube-asia.com/" target="_blank">Dispatch of Army:</a> FPS similar to Counter-Strike. A bit unstable.
<a href="http://www.youtube.com/watch?v=MK6zmMPBOyw&feature=related" target="_blank">Video</a>
<a href="http://www.gameogre.com/reviewdirectory/upload/Dispatch%20of%20Army.jpg" target="_blank">Screenshot</a>
<a href="http://softnyx.net" target="_blank">Wolfteam:</a> FPS that allows you to transform into wolves.
<a href="http://www.youtube.com/watch?v=jgtRAH7YRms" target="_blank">Video Link</a>
<a href="http://image2.sina.com.cn/gm/o/n/2007-04-05/U734P115T9D193201F167DT20070405163835_c.jpg" target="_blank">Screenshot</a>
<a href="http://red.planetarena.org/" target="_blank">Alien Arena</a> Fast-paced, arcade-like, futuristic FPS
<a href="http://www.youtube.com/watch?v=LMz1TAuG3Qk" target="_blank">Video Linkage</a>
<a href="http://www.winsoftware.de/screenshots/big/alienarenaue.jpg" target="_blank">Screenshot</a>
<a href="http://www.worldofpadman.com/" target="_blank">World of Padman:</a> Colorful FPS that is a modification of Quake 3 Arena. Features very unique gameplay.
<a href="http://www.youtube.com/watch?v=3ckfvUkiyR0" target="_blank">Video Link</a>
<a href="http://www.g4g.it/phpnews/images/world_of_padman_01.jpg" target="_blank">Screenshot</a>
<a href="http://www.airrivals.net/" target="_blank">AirRivals:</a> Formerly known as Space Cowboy, AirRivals an air combat game.
<a href="http://www.youtube.com/watch?v=p_CWwMD8xHk" target="_blank">Video Link</a>
<a href="http://static3.filefront.com/images/ycwwernmyf.jpg" target="_blank">Screenshot</a>
<a href="http://www1.rasterwerks.com/game/phosphor/beta1.asp" target="_blank">Phosphor:</a> Browser-based FPS. Contains just one map and has a small user base, but very impressive nonetheless (for a browser-based game).
<a href="http://www.youtube.com/watch?v=Ifrauvn_Fb0" target="_blank">Video Link</a>
<a href="http://techgurls.blorc.com/wp-content/phosphor.png" target="_blank">Screenshot</a>
<a href="http://www.quakeone.com/freequake/en.html" target="_blank">FreeQuake:</a> Just like the title suggests, this is free quake. This is a multiplayer-compatible shareware version.
<a href="http://www.quakeone.com/q1files/img/multiplayer.gif" target="_blank">Screenshot</a>
<a href="http://www.rising-eagle.com/" target="_blank">Rising Eagle:</a> Futuristic FPS that is graphically intensive, so system requirements are rather high, compared to the other listed games. Currently in open beta.
<a href="http://www.youtube.com/watch?v=Ko7WcHPr8JM" target="_blank">Video Link</a>
<a href="http://www.g4g.it/g4g/wp-content/uploads/2007/12/rise_eagle_demo_01.jpg" target="_blank">Screenshot</a>
<a href="http://sauerbraten.org/" target="_blank">Sauerbraten/Cube:</a> Mutiplayer as well as single player FPS. Maps are customizable, as it has a built-in map editor.
<a href="http://www.youtube.com/watch?v=1WPLKFI_ilE" target="_blank">Video Link</a>
<a href="http://www.g4g.it/g4g/wp-content/uploads/2007/12/sauerbraten_530.jpg" target="_blank">Screenshot</a>
<a href="http://assault.cubers.net/" target="_blank">Assaultcube:</a> Based off the cube engine, Assaultcube offers multiplayer gameplay in a more realistic environment. Very small download, only around 19 MB.
<a href="http://www.youtube.com/watch?v=45X5F_u_JNU" target="_blank">Video Link</a>
<a href="http://assault.cubers.net/pics/ingame_screens/ac_shot_23.jpg" target="_blank">Screenshot</a>
<a href="http://www.s2games.com/savage/" target="_blank">Savage: Battle for Newerth:</a> Fantasy-themed RTS and FPS hybrid.
<a href="http://www.youtube.com/watch?v=lqfS5vJ0P14" target="_blank">Video </a>
<a href="http://static4.filefront.com/images/etervkgjxn.jpg" target="_blank">Screenshot</a>
<a href="http://www.theprodukkt.com/kkrieger" target="_blank">.kkrieger:</a> Single-player only FPS that is a technological breathrough, as it just 96KB. Single-player only.
<a href="http://kk.kema.at/files/gfx/full5.jpg" target="_blank">Screenshot</a>
<a href="http://www.youtube.com/watch?v=1VqzjafwCNA" target="_blank">Video Link</a>
<a href="http://tremulous.net/" target="_blank">Tremelous:</a> Another Sci-Fi themed FPS. Named 2006 "Player's Choice Standalone of the Year" award by Mod DB, and recieved over a million downloads.
<a href="http://www.youtube.com/watch?v=QqdoRo5ndgI" target="_blank">Video Link</a>
<a href="http://www.marcofolio.net/images/stories/fun/games/fps/tremulous_screen3.png" target="_blank">Screenshot</a>
<a href="http://www.openarena.ws" target="_blank">OpenArena</a> Based off the ioquake3 engine, OpenArena is yet another game that shares similar gameplay to Quake III Arena, with the same core gameplay.
<a href="http://www.youtube.com/watch?v=p4o_ovlM5g8&feature=related" target="_blank">Video Link</a>
<b>Upcoming Games:</b>
<a href="http://www.battlefield-heroes.com/" target="_blank">Battlefield Heroes:</a> Schedules to be released this summer, Battlefield Heroes is a free, ad-supported shooter from the Battlefield team with a cartoony graphic style comparable to Team Fortress 2.
<a href="http://www.battlefield-heroes.com/videos/release-announcement" target="_blank">Introduction Video</a>
<a href="http://www.battlefield-heroes.com/images/introshots/small/scene3.jpg" target="_blank">Screenshot</a>
<a href="http://www.quakelive.com" target="_blank">Quake Live:</a> Developed by id Software, Quake Live will be ad-supported version Quake III Arena playable via web browser. No release date annouced.
No video available
All of the games have fairly low system requirements. I have not tried all the listed games, and thus my descriptions may seem a bit lacking.
The screenshot link and the spoiler the image under spoiler tags are the same.
<a href="http://urbanterror.net" target="_blank">Urban Terror</a>riginally a mod of Quake III Arena, UT is now a standalone game. Its gameplay is comparable to Counter-Strike
<a href="http://www.redwoods.net/images/urbanterror_ingame.jpg" target="_blank">Screenshot Link</a>
<a href="http://www.youtube.com/watch?v=0irPKekjzuA" target="_blank">Video</a>
<img src="http://www.redwoods.net/images/urbanterror_ingame.jpg" border="0" class="linked-image" />
<a href="http://warrock.gamersfirst.com/index.php" target="_blank">War Rock:</a> An FPS akin to Battlefield (or at least in my eyes). Features many vehicles. Free to play, but some items require money.
<a href="http://www.youtube.com/watch?v=bUBdg7pT5Lk" target="_blank">Video Link</a>
<a href="http://www.mmoginfo.com/imagenes/foto_war_rock.jpg" target="_blank">Screenshot</a>
<img src="http://www.mmoginfo.com/imagenes/foto_war_rock.jpg" border="0" class="linked-image" />
<a href="http://www.gunzonline.com/" target="_blank">Gunz: The Duel</a>: Not exactly an FPS (it's a third person shooter), but I though I'd include it anyway. Non-traditional shooter, but very fun
nontheless. Has some RPG elements as well, like leveling up. I'd recommend you try the north american version, as it has more game modes. Very large user base, with a few thousand on at any given time.
<a href="http://www.youtube.com/watch?v=jV8a0JUlfnw" target="_blank">Video Link</a>
<a href="http://i63.photobucket.com/albums/h146/Odinius/gunz_gross01.jpg" target="_blank">Screenshot</a>
<img src="http://i63.photobucket.com/albums/h146/Odinius/gunz_gross01.jpg" border="0" class="linked-image" />
<a href="http://www.joinfear.com/main" target="_blank">F.E.A.R. Combat:</a> This is the multiplayer portion of the commercial FPS Fear.
<a href="http://www.youtube.com/watch?v=HmOhqsbqs6I" target="_blank">Video Link</a>
<a href="http://xubanu.files.wordpress.com/2006/08/fear_big.jpg" target="_blank">Screenshot</a>
<img src="http://xubanu.files.wordpress.com/2006/08/fear_big.jpg" border="0" class="linked-image" />
<a href="http://www.ijji.com" target="_blank">Soldier Front:</a> Tactical shooter available on ijji website.
<a href="http://www.youtube.com/watch?v=hSsl5gAsJ4g" target="_blank">Video Link</a>
<a href="http://www.gameogre.com/reviewdirectory/upload/Soldier%20Front.jpg" target="_blank">Screenshot</a>
<img src="http://www.gameogre.com/reviewdirectory/upload/Soldier%20Front.jpg" border="0" class="linked-image" />
<a href="http://www.nexuiz.com/" target="_blank">Nexuiz:</a> Quake-style shooter. Very fast paced arcade-like shooter.
<a href="http://www.youtube.com/watch?v=4E5kRPp9m3E" target="_blank">Video Link</a>
<a href="http://shazbot.blogsome.com/wp-admin/images/nexuizDNAQualDetails.jpg" target="_blank">Screenshot</a>
<img src="http://shazbot.blogsome.com/wp-admin/images/nexuizDNAQualDetails.jpg" border="0" class="linked-image" />
<a href="http://www.warsow.net/?page=home" target="_blank">Warsow:</a> Extremely fast-paced FPS with cel-shaded graphics.
<a href="http://www.youtube.com/watch?v=iB72-rCnuwk" target="_blank">Video Link</a>
<a href="http://www.gameogre.com/reviewdirectory/upload/Warsow.jpg" target="_blank">Screen</a>
<img src="http://www.gameogre.com/reviewdirectory/upload/Warsow.jpg" border="0" class="linked-image" />
<a href="http://www.planetwolfenstein.com/features/articles/pw_faq_et.shtml" target="_blank">Wolfenstein: Enemy Territory:</a> War based FPS, highly polished. Fairly large community.
<a href="http://www.youtube.com/watch?v=GIeH7h0HTlk" target="_blank">Video Link</a>
<a href="http://i.d.com.com/i/dl/media/dlimage/59/13/5913_large.jpeg" target="_blank">Screenshot</a>
<a href="http://www.americasarmy.com/" target="_blank">America's Army:</a> Tactical FPS sponsored by the US military.
<a href="http://www.youtube.com/watch?v=Z6SVueaI-cM" target="_blank">Video Link</a>
<a href="http://static.howstuffworks.com/gif/americas-army-3.jpg" target="_blank">Screenshot</a>
<img src="http://static.howstuffworks.com/gif/americas-army-3.jpg" border="0" class="linked-image" />
<a href="http://doa.cube-asia.com/" target="_blank">Dispatch of Army:</a> FPS similar to Counter-Strike. A bit unstable.
<a href="http://www.youtube.com/watch?v=MK6zmMPBOyw&feature=related" target="_blank">Video</a>
<a href="http://www.gameogre.com/reviewdirectory/upload/Dispatch%20of%20Army.jpg" target="_blank">Screenshot</a>
<img src="http://www.gameogre.com/reviewdirectory/upload/Dispatch%20of%20Army.jpg" border="0" class="linked-image" />
<a href="http://softnyx.net" target="_blank">Wolfteam:</a> FPS that allows you to transform into wolves.
<a href="http://www.youtube.com/watch?v=jgtRAH7YRms" target="_blank">Video Link</a>
<a href="http://image2.sina.com.cn/gm/o/n/2007-04-05/U734P115T9D193201F167DT20070405163835_c.jpg" target="_blank">Screenshot</a>
<img src="http://image2.sina.com.cn/gm/o/n/2007-04-05/U734P115T9D193201F167DT20070405163835_c.jpg" border="0" class="linked-image" />
<a href="http://red.planetarena.org/" target="_blank">Alien Arena</a> Fast-paced, arcade-like, futuristic FPS
<a href="http://www.youtube.com/watch?v=LMz1TAuG3Qk" target="_blank">Video Linkage</a>
<a href="http://www.winsoftware.de/screenshots/big/alienarenaue.jpg" target="_blank">Screenshot</a>
<img src="http://www.winsoftware.de/screenshots/big/alienarenaue.jpg" border="0" class="linked-image" />
<a href="http://www.worldofpadman.com/" target="_blank">World of Padman:</a> Colorful FPS that is a modification of Quake 3 Arena. Features very unique gameplay.
<a href="http://www.youtube.com/watch?v=3ckfvUkiyR0" target="_blank">Video Link</a>
<a href="http://www.g4g.it/phpnews/images/world_of_padman_01.jpg" target="_blank">Screenshot</a>
<a href="http://www.airrivals.net/" target="_blank">AirRivals:</a> Formerly known as Space Cowboy, AirRivals an air combat game.
<a href="http://www.youtube.com/watch?v=p_CWwMD8xHk" target="_blank">Video Link</a>
<a href="http://static3.filefront.com/images/ycwwernmyf.jpg" target="_blank">Screenshot</a>
<img src="http://static3.filefront.com/images/ycwwernmyf.jpg" border="0" class="linked-image" />
<a href="http://www1.rasterwerks.com/game/phosphor/beta1.asp" target="_blank">Phosphor:</a> Browser-based FPS. Contains just one map and has a small user base, but very impressive nonetheless (for a browser-based game).
<a href="http://www.youtube.com/watch?v=Ifrauvn_Fb0" target="_blank">Video Link</a>
<a href="http://techgurls.blorc.com/wp-content/phosphor.png" target="_blank">Screenshot</a>
<img src="http://techgurls.blorc.com/wp-content/phosphor.png" border="0" class="linked-image" />
<a href="http://www.quakeone.com/freequake/en.html" target="_blank">FreeQuake:</a> Just like the title suggests, this is free quake. This is a multiplayer-compatible shareware version.
<a href="http://www.quakeone.com/q1files/img/multiplayer.gif" target="_blank">Screenshot</a>
<a href="http://www.rising-eagle.com/" target="_blank">Rising Eagle:</a> Futuristic FPS that is graphically intensive, so system requirements are rather high, compared to the other listed games. Currently in open beta.
<a href="http://www.youtube.com/watch?v=Ko7WcHPr8JM" target="_blank">Video Link</a>
<a href="http://www.g4g.it/g4g/wp-content/uploads/2007/12/rise_eagle_demo_01.jpg" target="_blank">Screenshot</a>
<img src="http://www.g4g.it/g4g/wp-content/uploads/2007/12/rise_eagle_demo_01.jpg" border="0" class="linked-image" />
<a href="http://sauerbraten.org/" target="_blank">Sauerbraten/Cube:</a> Mutiplayer as well as single player FPS. Maps are customizable, as it has a built-in map editor.
<a href="http://www.youtube.com/watch?v=1WPLKFI_ilE" target="_blank">Video Link</a>
<a href="http://www.g4g.it/g4g/wp-content/uploads/2007/12/sauerbraten_530.jpg" target="_blank">Screenshot</a>
<img src="http://www.g4g.it/g4g/wp-content/uploads/2007/12/sauerbraten_530.jpg" border="0" class="linked-image" />
<a href="http://assault.cubers.net/" target="_blank">Assaultcube:</a> Based off the cube engine, Assaultcube offers multiplayer gameplay in a more realistic environment. Very small download, only around 19 MB.
<a href="http://www.youtube.com/watch?v=45X5F_u_JNU" target="_blank">Video Link</a>
<a href="http://assault.cubers.net/pics/ingame_screens/ac_shot_23.jpg" target="_blank">Screenshot</a>
<img src="http://assault.cubers.net/pics/ingame_screens/ac_shot_23.jpg" border="0" class="linked-image" />
<a href="http://www.s2games.com/savage/" target="_blank">Savage: Battle for Newerth:</a> Fantasy-themed RTS and FPS hybrid.
<a href="http://www.youtube.com/watch?v=lqfS5vJ0P14" target="_blank">Video </a>
<a href="http://static4.filefront.com/images/etervkgjxn.jpg" target="_blank">Screenshot</a>
<img src="http://static4.filefront.com/images/etervkgjxn.jpg" border="0" class="linked-image" />
<a href="http://www.theprodukkt.com/kkrieger" target="_blank">.kkrieger:</a> Single-player only FPS that is a technological breathrough, as it just 96KB. Single-player only.
<a href="http://kk.kema.at/files/gfx/full5.jpg" target="_blank">Screenshot</a>
<a href="http://www.youtube.com/watch?v=1VqzjafwCNA" target="_blank">Video Link</a>
<img src="http://kk.kema.at/files/gfx/full5.jpg" border="0" class="linked-image" />
<a href="http://tremulous.net/" target="_blank">Tremelous:</a> Another Sci-Fi themed FPS. Named 2006 "Player's Choice Standalone of the Year" award by Mod DB, and recieved over a million downloads.
<a href="http://www.youtube.com/watch?v=QqdoRo5ndgI" target="_blank">Video Link</a>
<a href="http://www.marcofolio.net/images/stories/fun/games/fps/tremulous_screen3.png" target="_blank">Screenshot</a>
<img src="http://www.marcofolio.net/images/stories/fun/games/fps/tremulous_screen3.png" border="0" class="linked-image" />
<a href="http://www.openarena.ws" target="_blank">OpenArena</a> Based off the ioquake3 engine, OpenArena is yet another game that shares similar gameplay to Quake III Arena, with the same core gameplay.
<a href="http://www.youtube.com/watch?v=p4o_ovlM5g8&feature=related" target="_blank">Video Link</a>
<img src="http://upload.wikimedia.org/wikipedia/commons/thumb/5/53/OpenArena-Rocket.jpg/750px-OpenArena-Rocket.jpg" border="0" class="linked-image" />
<b>Upcoming Games:</b>
<a href="http://www.battlefield-heroes.com/" target="_blank">Battlefield Heroes:</a> Schedules to be released this summer, Battlefield Heroes is a free, ad-supported shooter from the Battlefield team with a cartoony graphic style comparable to Team Fortress 2.
<a href="http://www.battlefield-heroes.com/videos/release-announcement" target="_blank">Introduction Video</a>
<a href="http://www.battlefield-heroes.com/images/introshots/small/scene3.jpg" target="_blank">Screenshot</a>
<img src="http://www.battlefield-heroes.com/images/introshots/small/scene3.jpg" border="0" class="linked-image" />
<a href="http://www.quakelive.com" target="_blank">Quake Live:</a> Developed by id Software, Quake Live will be ad-supported version Quake III Arena playable via web browser. No release date annouced.
No video available
<img src="http://static.computergames.ro/cg/assassin/images3/quakelive/quakelive002.jpg" border="0" class="linked-image" />