Any PC Games with co-op?

[AgaBoogaBoo]

It might be fun to play with some friends through the levels online

 

[Frodolives]

System Shock 2 is still fun for it's age, and there is coop. Reportedly someone even made a coop for Deus Ex, but the file is no longer posted

 

[Lonyo]

C'mon, your a lifer, you should know the drill already.
Previous thread
Other slightly different thread

 

[notfred]

Any game with CTF or other team games is *sort-of* a co-op game, right?