Cooperative multiplayer games for PC or Xbox 360?

-Me and 2 other friends are having a night of gaming together and we want to play some cooperative multiplayer games. Stuff that's really team based and requires you to rely on each other to get anywhere in the game. We've already got Left 4 dead, but something similar would be good.



Thanks.Black ops(with multiplayer zombies,very funny:)),Battlefield bad company 2 or wait in november for MW3 or battlefield 3