Have you ever played The first Call of Duty: Modern Warfare? If you have, it's pretty much a zombified version of the AC-130 mission in the sp campaign. If not, well, picture being a gunner in an airplane which circles over an area repeatedly. You have cannons and machine guns, it's nighttime, and using night vision cameras, your goal is to kill as many zombies as possible while protecting civilians. Repeatedly. Personally, I consider it more of a novelty than a game.