Probably my favorite game from E3: a new rhythm game from Harmonix that puts a new spin on the whole music game genre. While the game does have your traditional "hit the mark with the right timing" gameplay, it also allows the user to change the song as they play it. Ultimately this conductor game should be seen to be believed. Check out this video for a good look (the gameplay starts around 3:40).
The game incoporates its Fantasia license loosely, but attempts to capture the spirit of the classic movie more than anything. Fantasia: Music Evolved comes out for Xbox One and Xbox 360 sometime in 2014, and requires Kinect to play.