I'm always interested in reading about co-op games, here's a nice recent list from one of my favorite gaming blogs, Rock Paper Shotgun. For me, the game of choice is Sniper Elite 2.
Quote
Sometimes you need a hand to hold, so we’ve compiled a list of the 25 best co-op games to play on PC with a headset-wearing friend or a muted stranger.
Whether solving puzzles, sneaking, shooting zombies or stabbing mythical creatures in the face, the existence of another player adds an element of unpredictability. The reality of your co-op partner constantly alerting the guards is drowned out by the experience in your head – the synchronised stealth takedowns, the perfectly executed plan – but both success and failure are more compelling when you can take credit for the former and blame someone else for the latter.
