Whether people know about this or not, I found a glitch that is a potential game destroyer for those who like to knife other players mid-game. While I was playing with my nephew in Shangri-La, he had downed himself with a frag grenade (typical antics of a mischievous player), and as I tried to save him, I had taken a hit from a stray zombie, but managed to kill it. As I attempted to re-revive him while, he knifed me, and I had gotten knocked down, thus ending the game. If a player takes any amount of damage and is knifed by a fellow player who is downed, it will knock yourself down, and could result in a game over. And I have tested this glitch on all of the zombie maps and it has worked on each one, (excluding the WaW revisited maps).