Instructions
Start "Call Of Duty: Black Ops" and select the "Zombies" mode. In this mode players must survive alone or with friends against groups of zombies.
Select the zombie map you want to play on and wait for the level to load. The Cymbal Monkey is available on all of the "Zombies" maps except for Call of The Dead and Ascension.
Kill zombies to acquire points. Go for headshots or lethal melee kills to get the most points. Damaging zombies or hitting their limbs gives you fewer points.
Continue killing zombies until you have nine hundred and fifty points, and then make your way to the mystery box. It spawns at different points on each map, but is easily identifiable by the blue glow that surrounds it and the question marks on the lid.
Stand in front of the box and hold down the "X" button on Xbox 360 ("F" on the PC version and "Square" on the PS3) until the box has cycled through a random selection of weapons. It takes a few seconds for this process to complete so make sure there are no zombies nearby before you start.
Pick up the Cymbal Monkey if it is chosen as the random weapon. If the game does not select it, wait ten seconds for the box to reset and then try again. You will have to pay the points again no matter if you picked the weapon up or not.