PC Multiplayer to buy for Steam Summer Sale

Hey all duders,I recently just moved away from several buddies that I used to play boardgames/video games (local) with. We all have different systems, with the only common one being Steam on the PC. To that end, I was wondering your thoughts for the best multiplayer (3 player minimum, any genre) games that are out that we should keep our eye on during the Steam sale. Any help would be totally awesome!

Co op or competitive?

Left 4 Dead 2, Borderlands 2, and Torchlight 2 for co op.

Counter Strike Global Offensive and Team Fortress 2 for competitive.

@believer258: Ah, yeah good question. Generally we head for the co-op option. Though that is not a definite. Thanks for the suggestions.