6. Hugo Strange
Dr. Strange is renowned for being one of the first enemies of to deduce the identity of Batman. For that alone, he has garnered quite a cult following in the Caped Crusader's history. Recently, Strange had a very significant part in the video game, Batman: Arkham City, as he was the one behind the prison's construction and even managed to make Bruce Wayne an inmate.
Why we shouldn't expect them: There was a short period of time where Tom Hardy's role in The Dark Knight Rises was unknown, but spy pics made a pretty substantial argument that he would be playing Dr. Strange. That obviously turned out to be false, but if anyone could have made this mad scientist work in film, it would have been Nolan. Of course, he could still show up in another series (and if he does, please let Robin Williams do it!), but if a psychological director like Nolan passed him over, then I wouldn't hold my breath.