Seems that Square Enix really wants Xbox 360 owners to buy Final Fantasy XIII-2 for that console over the PlayStation 3, as they announced today that there will be DLC exclusive for that system.
Before all you PS3-owners get too much in a tizzy, you can relax in knowing that it's just a weapon addition and not campaign content.
The weapon, called Azrael, is a special bow for Serah that Square Enix and Microsoft designed collaboratively.
This weapon is named after an angel who represents spirits and death. It is believed to possess the power to change the owner's destiny, and your Chain Bonus is upgraded when equipped. Serah alone has the ability to wield this legendary weapon. The player can obtain this weapon from Chocolina merchants, from Episode 2 onwards in the main game for 80 Microsoft Points via Xbox Live Marketplace for Xbox 360. Only Serah has the ability to wield this legendary weapon.
Azrael will be available for download on February 7, 2012 for 80 MSP ($1), just four days after the game's launch on January 31, 2012.
[Source]