I have been playing a lot of Left 4 Dead 2 Versus. I have found that trying to find a good team, and dealing with the idiots in that community, to be sort of like a psychological adventure game. It can be just as much (if not more) fun listening to the whining and b*tching, than playing the game itself.
Also some Global Agenda and Tribes:Ascend, mostly for one thing: JETPACKS!