Backstory: One of Bruce Wayne's childhood friends who only wished his parents had been killed when he was a child. Racked with jealousy over Wayne's own orphaning, he later sought revenge as an adult after he discovered Wayne's secret identity.
Why we want to see him: He's the latest major villain to be added to Batman's rogue's gallery -- he first appeared in 2002 -- but he has a strong connection to Wayne's early years, which were briefly explored in "Batman Begins." Having him return for the third movie in this supposed trilogy would do a lot to bring the story full-circle.
Casting suggestions: Nolan has worked with many of the same actors multiple times. Michael Caine and Bale came with him to his Victorian-era magician thriller "The Prestige." So why not bring Bale's rival from that film, Hugh Jackman, to play his rival once again?