Just my two cents, but I would have had Scarecrow in the Penguin's place. I was thinking about the Riddler but he is too unique in terms of his methods and lifestyle of criminality. Penguin is interesting but I think Dr. Jonathan Crane (no relation to Dr. Frasier Crane) is perhaps, aside from Joker and Two-Face, the most interesting. Like all Batman villains, he knows how to mess with his victims' (and Batman's) minds but fear itself makes him rather exceptional.