Mission-Numbers: On the mission numbers when you get to the part where you get to 
choose a weapon after moving the refregerator from the wall theres' a radio station
player on your left. Then theres' a tape on it. Hold down x (Only for Playstation 3). 
Then the tape will go into the radio. Then your screen will shake then the Thunder 
Gun will come out the wall.

To unlock DEAD OPS ARCADE go to the computer and type D.O.A.
To unlock all the story mode maps including the zombie maps go to the computer and type 3ARC UNLOCK.
To unlock all of the intels from the campaign go to the computer and type 3ARC INTEL UNLOCK.
To play the classic game ZORK go to the computer and type ZORK (you will also earn a trophy for it).