8. David Tennant - Mysterio
Thanks to his backstory, Mysterio - the expert magician and special effects genius - doesn't necessarily require a huge, hulking actor to play him, despite his most iconic appearance implying that he has the physique of an Olympic swimmer. He is a villain by choice - assuming they go with the Quentin Beck original version of the character - having decided his career as a Hollywood special effects wizard is a dead-ender, without any kind of military training and without the kind of background in the criminal underworld that would usually define more physical characters. And while he has hand-to-hand training thanks to his background as a stuntman, his biggest weapon, is his criminal brain. That is precisely what would make the former Doctor a good choice for the character: there has long been clamour from DC fans for the actor to be cast as The Riddler, and he has form in playing a creepy villain, thanks to his brief but show-stealing appearance as Barty Crouch Junior in Harry Potter & The Goblet Of Fire. Tennant would fit the image of the master strategist, and while he isn't exactly the most commanding of figures in terms of his physical make-up, combat training would bridge the gap in his skill set. What matters is his charisma, and his intellect, and Tennant would offer an intriguing performance in those respects.