There are a ton of zombie games in the App Store, some better than others. R.I.P. Rally is absolutely one of the better zombie-killing experiences out there. In this game, players use a variety of weapons, ranging from machine guns to flame throwers, to mow down the hordes of undead that appear. These weapons may be attached to one of several vehicles that also become weapons, giving players the ability to plow through wave after wave of zombie attack. While this is a freemium app, the in-app purchases are not overly intrusive, making this a very playable free game.