Modding games

[MuppetInvasion]

I am currently interested in making my own game for my computer, i want to make an FPS and base it on a game engine by someone else. Having already found out my computer does not like half life 2 (I didn't like the valve editor anyway) i want to find another game to mod. Please post any suggestions you have.

Criteria
-Not Half life 1/2
-Must be able to make my own models
-Must be able to make mod completely Separate from game world (So things like Fallout 3 and Oblivion i am not interested in).
-Must be able to make map without too much trouble with the editor.
-Must be an FPS or third person shooter even.

So i need links or suggestions to tools and games to make my mod.

 

[Diablo1123]

I think the Unreal Engine SDK came out for free a while back or something.

Found it : http://www.udk.com/

Also, if you could do Garry's Mod.

 

[MuppetInvasion]

That looks awesome

but do you know if it self-contains all the tools or if i have to look around for 3d modeling tools and converter and all that. (though that is highly unlikely.)

 

[Diablo1123]

Can't say, I haven't tried it. I might one day.