Worms Armageddon (Worms game, 'nuff said.)
Medal of Honour: Allied Assault (FPS)
Armagetron (Awesome Light Cycles game, here: http://www.armagetronad.net/)

 

Well, if you like sports, play Fifa, NBA or Madden or something like that.

Further, RollCage 2, Age of Empires 2, Carmageddon 2, GTA 2 and Dungeon Keeper 2
Those are some old games, but really fun to play, and especially in LAN.

And offcourse the Call of Duty series
And Rainbow Six Vegas, really fun in co-op

 

Counter-Strike (original, pre-Steam)
Starcraft
Warcraft III
Diablo II
Quake III Arena

These are the ones I remember playing on my friend's lan back in high school.

 

Wow Thanks for all the suggestions

 

SYSTEM SHOCK 2!!!

4 Player Co-op It's amazing and creepy as hell. It'll keep you entertained for hoursssssssssss. Maybe even days.

;D

 

http://www.teewars.com/

Used to play this on school in my IT lessons. Believe me, it's worth playing!

 

I might mention that now we are on the PC it is the exclusive domain of first person shooters and while halo probably should be king of the console FPS it pails when compared to some of the stuff out there.


Back on topic I find myself in the same situation, normally I just raid the £/$10 game racks although recently I have been checking out the free games and I am liking what I see.
I really hate linking wikipedia but it is kind of hard to mess up links to bad so I will make an exception:
http://en.wikipedia.org/wiki/List_of_free_...person_shooters

Going this way your "old" computers (or laptops) can also join in/act as a server as well and no matter the game I find the more people are there the more fun it is.

@CPhantom I am confused.

 

Lol used to do that at school.
I burned 5 CDs with WinRar self extract versions of CS 1.6 wtih as much stuff removed as possible so the installs would be fast
Then we'd play LAN with 20 people for an hour

Too bad that teacher retired