The ending, as described by Meaty:
NO JOHN, YOU ARE THE ZOMBIES.
And then John was a zombie.
That's how anti-climactic. My roommate not only agreed, but I actually knew he'd finished the game when I heard him going apeshit in the next room.
Kalgorn: Chris played it on PC, and he said it was awesome the BS ending aside. He went through all three games in the last three weeks that way, and he's actually an XBOX/PS3 kind of guy.