The new Call of Duty : Black Ops has a few hidden extras that can be accessed from the electric chair in the main menu screen.
To gain a few more achievements and access the new content you first have to get out of the straps on the chair by pressing LT and RT over and over. Watch the video after the jump for the other unlocks.
Typing DOA, into the PC will unlock a funky Dead Ops Mode a retro top down game with co-op mode, that you can later access it on the main menu screen via Zombie.
Via Softsailor