David Tennant as re-imagined Riddler plz.
Yeah I've heard this rumor a lot as well.
I think it would be a risk to cast him in such a high profile film in his first hollywood outing - but if it did happen I'm sure he'd be excellent.
Coincidence corner - both Tennant and Heath Ledger have played Casanova.
I always wanted to see Tennant's Dr Who predecessor, Chris Eccleston, as The Joker, but even he would have been hard placed to top Mr Ledger's performance. Personally, I want to see the Riddler played by someone small, smug, intelligent and creepy, like David Hyde-Pierce (Niles in Frasier) or the guy who plays Ben in Lost.