Left 4 Dead

Left 4 Dead is mostly fun when played cooperatively and the game will fulfill your wish of being caught in a Zombie Apocalypse from both perspectives with tons of guns and hordes of Zombies at your disposal. Unpredictable & relentless enemies make it imperative to have human teammates in harder difficulty modes, but you can't complain about killing zombies alone either. The game also offers a variety of gameplay modes which will keep you interested for a while.