Diablo 3 "Horadic Cube" app, which possesses the power to combine your phone's applications into super applications. Or how about the new Kinect functionality for StarCraft 2? Not since Dance Central: The Krump Imperative have we seen such feverish flailing.
The best of the bunch is clearly the World of Warcraft update, which not only adds a new, pitch-black dungeon, but also a "Dungeon Helper" named Crabby, who assists you in navigating the game's instances. Go get acquainted with your new crustacean cohort -- but we wouldn't suggest letting Clippy find out. That dude's jealous as all get-out.