I finished COD Ops last night on "regular" and this morning was looking for other "goodies" for this awesome game and found this. Enjoy.
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Hint: Pack-A-Punch on Five (Zombies)
If you want to reach the Pack-A-Punch on the Zombies mode "Five" map:
Make a crawler and go into the middle room and adjust the DEFCON level to DEFCON 5. Every teleporter will take you to Presidential Suite. All switches are in that room -- 3 are upstairs and 1 is downstairs.
Cheat: Codes
On the Main Menu, alternately tap RIGHT and LEFT triggers. After about 5 taps a piece, you'll stand up. Leave your seat and examine the back wall. A small black and white computer terminal can be found here. Approach it and enter these codes using the on-screen keyboard in the "Central Intelligence Agency Data System."
DOA - Play the super-awesome top-down Smash TV-style Dead Ops Arcade minigame
3ARC INTEL - Unlocks all the intel in the game for viewing (Disables Closer Analysis Trophy/Achievement)
3ARC UNLOCK - Unlocks all levels and Zombie Mode levels
ZORK - Unlocks Zork I: The Great Underground Empire (an incredibly great text adventure from 1980) which you can play on the console (!)
HELP - Gives you a list of commands to interface with the console -- you can check mail messages and perform other mundane functions, some of which are listed below
DIR - Gives a list of audio files and pictures which you can open with the CAT command (e.g. CAT NoteX.txt)
WHO - Gives a list of login names for use with the RLOGIN function (but they require a password)
Unlockable: Pentagon Map for Zombie Mode (Five)
Beat the game on any difficulty to unlock Zombie Mode, where you play as Nixon, Castro, Kennedy, McNamara, beat the game on any difficulty. Alternately, you can enter the 3ARC UNLOCK code in the cheats menu.