Various Black Ops 2 Glitches:
Apparently, you can get God Mode (i.e. invincibility) on the zombies game mode.
SVU Sniper Glitch
Sometimes, SVU bullets will actually go through the player model, even if you're on target. This seems to be a bug.
XBox 360 mods
Looks like somebody has already figured out a way to run mods/hacks on the multiplayer. In this video, it looks as if he can jump as high as he wants to. Also looks as if he's completely invincible and has unlimited ammo:
This was present in the previous game. Using the ballistic knife, you can make it look as if your player is floating along the ground:
Nuketown 2025 - Zombies Glitch
If you jump up on a certain part of the map in Nuketown 2025, the zombies will be unable to kill you.
Thermal / Night Vision
A bug in the game allows you to get night vision (PS3 and XBox) if you have 3 killsteaks: