1). Log into Black Ops 2.
2). Load the multiplayer menu up and as soon as you do scroll down and select the system link option, you are then to create a game.
3). Quickly select Create a Class, then the first class.
4). You should shortly after hear a sound notifying you that you've signed into live.
You'll also see the game version update.
5). Back out after hearing this and select Xbox LIVE. It should notify you telling you that your stats have been reset, however it will effect nothing.

Warnings/Notes: If you are disconnected from live while doing this, it will reset your stats. You must do this quickly, but not too fast. Based off of experience this only seems to work for prestiged accounts, however I did not put this through extensive testing. This will mess with your custom classes, if you get a gun in your tactical slot it'll cause your Xbox to freeze and you'll have to re-do this. I am not responsible if you accidentally reset your stats. You will NOT receive everything at one time, if you receive what you desire, then I recommend you to stop doing it.