Limbic Software has Zombie Gunship (iTunes Link) for the iPhone and iPod Touch in the iTunes App Store for FREE for a limited time.

JUST UPDATED with an all new scenario and AirPlay mirroring support, Zombie Gunship puts you in the gunner seat of a heavily-armed AC-130 ground attack aircraft. Strategically fire your powerful guns to slay endless waves of zombies and protect the remaining survivors of the zombie apocalypse!