Now here's an interesting game that shows a lot of promise: Ultimate Finger [App Store].
At first glance, it seems like it may just be another whack-a-mole tapping game, which happens to come in a nice package. As it turns out, the developers have added a number of interesting elements that expand significantly on the gameplay.
The premise of the game is that you are the guardian of a powerful Crystal which you must defend against monsters who hope to use it to destroy the world. The Crystal is in the middle of a field centered on your screen. You must defend against goblins, werewolves, trolls, and wizards. As guardian, you have a certain amount of magical power that can be used against the invading enemies. These come in 3 different attacks which are invoked with on-screen gestures:
The Thunder - tapping on the screen
The Pillar of Fire - dragging your finger on the screen
The Explosion - drawing a circle on the screen