Cheat Codes for Batman Arkham City (Xbox 360)

Cheats
2 Cheats

Left, Left, Down, Down, Left, Left, Right, Up, Up, Down
 * Unlock All Alternative Skins

Use the Cryptographic Sequencer, hold down all shoulder buttons (don't let go), rotate the left stick counter-clockwise and the right stick clockwise. After a few seconds the mode will activate. This can be activated at anytime during gameplay "without" the Cryptographic Sequencer as long as you complete the game on Normal. It can be activated in Riddler's Revenge as well and New Game Plus at anytime.
 * Big Head Mode

Unlockables
2 Unlockables

In order to unlock the alternate ending, you must have the Catwoman DLC. In her third mission when you have the option to go left or right with the "loot," head right for the alternate ending. Don't worry; you'll be able to "rewind" back and not ruin anything in the main game. Complete Batman: Arkham City on Normal or Hard difficulty to unlock New Game + Mode where you will retain all of your gadgets and XP. Several things are different in the New Game +:
 * Alternate Ending
 * New Game +

- No counter icons on thugs.

- Different Thug Levels: Tougher thugs are available from the start of the game.

- Different Thug Configuration.

- Increased Difficulty Bosses: Bosses will be even more cunning.

Easter Eggs
6 Easter Eggs

If you look closely in one of Deadshot's storage closets, you'll see that he has a lightsaber (an apparent reference to the fact that Mark Hamill, the voice actor for the Joker, also voiced Luke Skywalker in the original Star Wars trilogy). After you fight the "Joker" in the Steel Mill area, you'll need to return to retrieve the cure. Enter Detective Mode when you do. You should notice that the Joker's corpse doesn't actually have a skeleton, just like Clayface didn't when you defeated him in Arkham Asylum. That's some really cool foreshadowing that gives players a glimpse of what to expect at the end of the game, if they're paying close attention. When you get to the mission when you have to get the cure back from Joker you get to a part where a video plays and he rants about The ending to the show LOST. In Two Face's courthouse, if you enter through the back door and go downstairs, Calendar Man is locked in a cell, and you can interact with him like many other villains locked up across the city. But with one difference. If your system clock is set to a holiday, Calendar Man will have a speech about that holiday when you interact with him. To see all the dates he has speeches for, simply look to the right of his cell. Against the wall is a calendar with all of the dates circled in red.
 * Star Wars Reference (Lightsaber)
 * Secret Foreshadowing (Spoilers)
 * Lost Reference
 * Holiday Greetings from Calendar Man
 * Hidden Cryptographic Sequencer Message

If you use the cryptographic sequencer and tune in anywhere in the general range of 700.00/500.00, you will hear a disembodied voice repeating a sequence of numbers over and over. Every time the sequence ends a tone chimes, and then the number sequence starts over again. The numbers are 9 23 9 12 12 18 5 20 21 18 14 2 1 20 13 1 14. If you assign a letter to each number (A=1 B=2 C=3 etc.), the message translates to "I WILL RETURN BATMAN."

On station 500.00/900.00 you get a different numeric string:

5 15 9 7 21 18 18 14 3 5 24 15 12 7 22 3 10 5 15 9 22 3 8 25 26 15 16 25 10 15 17 25 *music chime* repeats. This can be decoded as "YOU WILL PAY FOR WHAT YOU HAVE DONE TO ME." In the Warden's Office, head back to the room with the Warden's portrait on the far wall. Turn left as soon as you enter the doorway and approach the wooden wall. You can destroy this with Explosive Gel. It may take a bit of trial and error, but one panel can be blown away. Beyond this is an unmarked room with a blueprint on the wall. It shows plans for the relocation or expansion of Arkham to Gotham City. This is a nod to the setting of Batman: Arkham City. For video and images of this Easter Egg, check out IGN's article, Warden Sharp's Plans For Arkham City.
 * Reference to Batman: Arkham City in Arkham Asylum

Achievements
1 Achievements
 * Calendar Man Dates

Here are the dates you can visit Calendar man for a special message. On each day he describes a murder and crosses the day off the big calender to his left. You can make this faster by just disconnecting from Xbox Live and setting your date and time to the correct dates.

- January 1st

- Feburary 14th

- March 17th

- April 1st

- May 8th

- June 19th

- July 4th

- August 16th

- September 5th

- October 31st

- November 24th

- December 25th

Source
http://uk.ign.com/cheats/games/batman-arkham-city-xbox-360-55051