Game Director, Sefton Hil tells fans,
We have had an amazing release of Batman: Arkham City and we wanted to thank you all for your incredible support before, during and after the game’s release.
As a token to our appreciation, we’ll be offering a brand new, totally super sweet, Batman Inc. Batsuit skin absolutely free!
Along with the free skin come the ability to now use it along with all other skins in the campaign whether you beat the game or not by means of a cheat code.
To unlock this, simply press the following combination on the Main Menu screen (after you have selected your save slot):
– Left, Left, Down, Down, Left, Left, Right, Up, Up, Down.
You will get an audio confirmation and when you continue your game, you will get the option to select your favorite skin.
We will be sure to update you as further details are revealed.
Source: Batman Arkham City Community