League of Legends. The new Co-op vs. AI mode allows players to team up against an opposing group of computer-controlled opponents. The mode features "newly overhauled" AI and two levels of difficulty, and still awards players with XP and IP (points used to make in-game purchases).
Riot's Travis George promises the AI will "put up a fight" and will use "coordinated teamwork and advanced tactics." In case you don't believe him, Riot posted a video recap of a recent match played by its own staff, in which the people who made the game lost handily to their own creation. Find the video after the break.