#8 Red Dead Redemption
This open-world adventure, set in the wild west of 1911 see John Marston, a former bad boy, attempt to hunt down his old buddies when his wife and son are taken by the government and used as leverage. This is what you get for trying to stay on the lawful straight and narrow, apparently.
John must track them through the desert, hunting and skinning animals, collecting herbs and winning money through gambling along the way. In co-op mode, however, this almost feels like I completely different game. Up to 16 players can join, and the balance of competitive versus cooperative comes down to the very nature of the players as they must choose to form posses, work together towards goals, or sabotage each other.