ZombiU has been rated M, and was provided with this description:
In this survival horror game, players assume the role of London inhabitants in the wake of a zombie invasion. From a first-person perspective, players scavenge the city and use realistic firearms, explosives, and melee attacks to kill waves of zombies; battles are highlighted by loud shrieks, impact sounds, and large splashes of blood. Players can also perform finishing moves to dispatch downed zombies: stomping on/bashing in their heads in with a cricket bat. Attacks often result in decapitated/dismembered bodies, and dead enemies continue to incur damage when shot. The words “f**k” and “sh*t” can be heard in the dialogue.
And maybe I’m just immature, but they make it sound like all kinds of awesome.