7 Cities TD ($2.99 -> $0.99) – This tower defense was one of the first in the App Store right next to Fieldrunners and is still one the best available. I suggest this game to any tower defense fans who have not bought this game yet.
Guitar Rock Tour ($4.99 -> $2.99) – Similar to Guitar Hero, this game offers classical rock along with modern rock music with the choice between playing guitar and drums. The full version includes 17 songs.
DJ Mix Tour ($4.99 -> $1.99) – Another rhythm game from Gameloft that didn’t quite appeal to many, but for $1.99 it is worth checking out. The graphics and flash are quite good, gameplay is questionable. Try out the free version first.