If you like playing First Person Shooters and want to improve, then give FPS Training Zone a try. Swipe to aim like you would with a touch pad or mouse, press the shoot button as fast as you can, and try to hit the annoying little target. It's designed to move around much like an opponent would in a typical shooter.
As well as the basic training modes, there's the new and addictive Challenge mode. Challenge mode features a number of different levels, each with differently behaving targets. A lot of fun that will keep you coming back for more, and hopefully improving your skills for your next deathmatch.
It's cost free, ad free, and a tiny 1MB. Works great on iPhone 3G.