dekay.org

Tower defense games are perfectly suited for the iPhone as they fall somewhere right in between turn-based and real-time strategy games. If you're unfamiliar, TD games are all about bad guys (usually called creeps) trying to get from one end of the screen to the other as you set up towers along the way in hopes of blowing them to bits before they get to their destination. There is usually time between waves so you can plan your defenses just right while not having to worry about obscuring the on screen action with your fingers.