Joseph Gordon-Levitt rumored to be Alberto Falcone, a.k.a. the Holiday Killer, in 'Dark Knight Rises'
But Comic Book Movie has reported that an insider tells them JGL is cast as Alberto Falcone, son of mobster Carmine Falcone. Carmine made an appearance in "The Dark Knight" (played by Tom Wilkinson) and in the DC universe, Alberto becomes a serial killer called the Holiday Killer, who is (naturally) an enemy of Batman.
In the comics, Alberto was born on Valentine's Day and when he starts killing citizens of Gotham, he attacks on holidays, hence his name, starting with Halloween, then Thanksgiving, Christmas, New Year's, Valentine's, St. Patrick's Day, April Fools, Mother's Day, etc.
The CBM post detailing this character has been removed, but several sites have used it as the source for this casting rumor. So take all of this with a grain salt.