Who knew that a Ninja's worst enemy could be fruit? Apparently, Halfbrick Studio, the developer of this popular game. Just swipe your finger to cleave flying fruit in two, ideally before they hit the ground. Oh, and keep a watch out for bombs; mistakenly slice one, and it's game over. The app is integrated with OpenFeint (so you can compete with your friends), and it's an ideal app for commuters or for those stuck in a slow-moving grocery store line.