Instructions
Launch the "Nazi Zombies" mini-game in "Call of Duty: World at War."
Kill a few zombies and raise some cash, because you will require some money for this method.
Move toward the room with "help" written on the door and enter. In this room you will find a box with a "?" on the side.
Observe the box, particularly the color of the "?" on it. When the "?" starts to turn a gold color open it quickly. It is important to do this quickly and as soon as there is any gold coloring because the box opening has a slight delay, and if you are not quick enough it will not work.
Utilize your new weapon. Depending on how many times you do the above, the special weapon varies from the alien ray gun to a BAR, FG42, and the M2 flamethrower, and eventually starting over again with the ray gun.