I am a sucker for augmented reality apps (AR) and therefore had to try out Mosquitoes right away when developer Makayama pointed me to it.
The iPhone game Mosquitoes lets you shoot animated mosquitoes that are infesting your room. The game uses besides the camera, the compass and accelerometer to realistically let you hunt down the mosquitoes around you.
Try playing this AR Game on a rotating office chair - it works quite well.

The Mosquitoes AR game has two modes. Shoot as many mosquitoes as you can in 2 minutes and precision shooting where you only have 10 bullets.

Similar games existed before that used the camera to augment animated insects on your surroundings, but with the compass the Mosquitoes in this game have a real location in the room.
The Mosquitoes AR game from Makayama for the iPhone 3GS is available now on iTunes for $0.99. If you have a U.S. iTunes account you can use the codes MNAREXJERFM4 and X43K4W9AYKAJ to get this game free.