We just spent the last half-hour running around the iPhone Alley offices, swinging our iPhones like tennis rackets, having a blast! What were we doing? Playing Air Tennis, of course! This awesome game from Unit9 [App Store, $0.99] lets you and a friend play rounds of virtual tennis, using your iPhones' as rackets. Linked via Bluetooth, one person serves while the other must hit the ball correctly to send it back. As you go back and forth, you can hear the ball whizzing towards you as a voice tells you which swing to use.
After playing Air Tennis and really getting into it, I just have to recommend that everyone goes out and gets it. It's that fun. Don't believe me? Check out the gameplay video below!