Games:
Dragonvale (I play this every freakin day)
Pocket Frogs
My Country
Robotek HD
TINY TOWER (omg love this game. same people who make pocket frogs)
LogosQuiz
Usefulness:
SoundHound
Sports Tracker (for workouts)
GifBoom (really fun!)
Ringtones (for making ringtones for your iPhone if you have one)
Um...I'm pretty sure all of those are free haha.