So, I bought Serious Sam HD TSE, and really enjoyed playing it online in a co-op game, and Alien Swarm was awesome. I really love co-op games and would like to know more about any other PC games with a co-op story/campaign/ mode. If they're free, or can have a multiplayer mode that can be played with just one PC, even better. Also, they don't have to be FPS's, any genre will do. Thanks in advance
