Probably one of my favorite gaming genres, Zombies!
I somehow don't really like Zombie games standalones but mostly as extra game modes.
In MW3, I mostly play Infected. In Halo, i mostly play Infection. In Black Ops and World at War, I mostly play Nazi Zombies.
How about you? Also, does anyone know good Zombie flash games? I know some fun ones for you, look them up on ArmorGames:
Infectonator: World Domination: Control the zombies and conquer the world. So much win.
Zombie Survival: I like the sprites and the shop but the area could be bigger, the shop could have more stuff and the zombies shouldn't be able to spawn so close to you. For the rest, funny little arcade game.