It's time. It's been five years since The Dark Knight was released and longer still since the death of Heath Ledger, whose performance as the anarchic Joker netted him a posthumous Academy Award (the only one yet conferred on an actor in a superhero film). Even considering the films that preceded it, the Spider-Man and X-Men franchises in particular, The Dark Knight was one-of-a-kind: critically acclaimed and the first superhero film to gross over $1 billion, it set the pattern for the genre, which has since gone from being a cinematic trend - such as Westerns were in the 1950s - to an almost unprecedented phenomena. While it's overstating it to lay all that success at the feet of one man, Ledger's role in The Dark Knight has become a touchstone for almost every villain since, from Javier Bardem's Silva in Skyfall to Benedict Cumberbatch's Khan in Star Trek Into Darkness. His influence has been all-pervasive, setting up an impossible expectation for whomever next is brave enough to play the Clown Prince of Crime. Still, with Batman vs. Superman fast approaching - its expected the role of the Caped Crusader may be recast in a matter of months - it's time to begin considering actors who might, perhaps, be willing to pick up the mantle of The Joker. After all, what's the point in introducing the expanded DC Universe if filmmakers aren't going to make the most of what it has to offer, which has to include Batman's nemesis. It's unlikely the Ace of Knaves will have much of a part to play in the coming sequel to Man of Steel - Batman vs. Superman is presumably all about the vs. - nevertheless, they'd be remiss not to at least start sizing up a new smile for the greasepaint. So without further ado, here are 10 of the best.