If you haven't beaten the single player campaign in Call of Duty: Black Ops - you'd only have one zombie map at your disposal for the four player co-op survival mode. If you didn't take the time to explore the menu area of the game, you'd also be missing out on the game's other co-op mode - Dead Ops Arcade - a top down shooter. Lucky for you, this weekend Activision is unlocking both of those options for a limited time.
DOA, or Dead Ops Arcade puts you and up to three other soldiers in a pursuit of the Cosmic Silverback; tracking him through a gauntlet of arenas filled with traps, treasure and waves of flesh-hungry zombies.
Five features four significant real-life figures from the Cold War era: John F. Kennedy, Robert McNamara, Fidel Castrol and Richard Nixon. They are all meeting in the Pentagon when zombies break in and start attacking.
After the weekend in over, things will go back to normal. But don't worry, unlocking Five is as simple as beating the game. Dead Ops requires a bit more work - but here's the scoop on how to do it.
To Unlock Dead Ops Arcade in Call of Duty: Black Ops:
You'll first need to get free of the chair in the main menu - while you're sitting in the chair hit the left and right triggers on your controller a few times. L, R, L, R, L, R, L, R, L, R!
From there head to the back of the room and find the small terminal computer.
Type DOA (and then pressing enter) - unlocks Dead Ops Arcade (located in the main Zombies menu once unlocked);
You can also enter ZORK to launch the classic text adventure, Zork.