To unlock Dead Ops Arcade, you must first get out of the chair by continuously pressing and . Then go to the computer that is in the far back of the room, and enter "DOA", then press enter on the far right of the keyboard. This will unlock Dead Ops Arcade.
Once in Dead Ops, run around the island portion on the outer edge letting all the zombies to bunch up. When a green Speed Boost power up appears, grab it and save it. Once there is a huge cluster of zombies, turn around towards the zombies and press to use the Speed Boost. This will make you fly across the screen killing tons of zombies.