Clay Shooter Mania is a clay-pigeon shooting game that uses the iPhone 4 accelerometer and gyroscope features to make for a unique gaming experience, but you're going to need room to move around to play it.
One of the more-amazing features of the iPhone 4 when it came out was the gyroscope, which enabled users to move the device and view an object as though the iPhone screen were a window into a different world. There have only been a few apps so far at the iTunes App Store that take advantage of this feature (Eliminate: GunRange, for example).
Clay Shooter Mania lets you shoot clay pigeons with a shotgun and uses gyroscope technology to give you a window into its target-shooting world. When a clay pigeon is launched into the air (Pull!), use the 3D radar in the upper right to determine which way you'll need to turn the iPhone (and your body) to take the shot. As you progress through levels, you'll be challenged to hit more clay pigeons in one pull, and some variations fly faster than others. Fortunately, you can use a bullet-time-like option that slows down the action for particularly difficult shots. Later, you can unlock the machine gun, which lets you hit more targets faster.
Clay Shooter Mania is a fun game when you have some space to play, but is not a good game (for obvious reasons) during your commute or really anywhere you're in a tight space. If you'd like to try a game that makes great use of the iPhone 4's gyroscope features or if you are a skeet-shooting fan, you should definitely check out this game.