PowerUp Heroes. If you own a Kinect, and do not own PowerUp Heroes then you need to do yourself a favor and go out and buy it. It's basically a comic book styled fighter that uses your avatars powered up with superpowers to fight each other. The single player campaign is ok, but the best part is versus mode. The tracking isn't exactly perfect, but at least whenever I play, it's done a fantastic job picking up not only my movements, but the movements of my opponent as well. It's always been a ton of fun to play, and it's something that I definitely keep it around for parties and stuff like that.
Plus, the lightning suit's main power is a basic ball of lightning that you use by motioning like the Kamehameha, and the ninja suit allows you to basically use Scorpion's chain attack from Mortal Kombat. It's amazing.