Call of Duty: World at War: Zombies for your Apple-branded mobile device? First of all, fence straddling is dangerous. Get down from there! Also, there's no reason to be all wishy-washy anymore, as a free "Lite" version of the game has recently become available on the App Store.
Zombies Lite allows players to mow down three rounds of oncoming Nazombies in a single-player match, or two waves of the undead in a multiplayer match before coming to an abrupt end. That may come off as a little unsatisfying, but hey -- 'tis better to have murdered zombies and lost than to have never murdered zombies at all.