Check out my game, Zombonic. It was released late last year and has since undergone a number of updates which have added extra levels, leaderboards and other general improvements. There is a Lite and Paid version available.
The game is played in first person, although it's a bit different to what you would expect from the standard FPS. You look around using the gyroscope and tap targets on the screen to shoot them. Zombies will approach you from every angle and you have to kill them before they can reach you; if they grab you, it's all over. The aim of the game is to hold out for as long as you can and accumulate as many points as possible before you are finally overwhelmed. Be on your guard - they have a way of creeping up on you!