I'd go with Voldemort. That mofo is just cool.
Movies based on books ruin the characters for me, so not counting the movies, my favorite is either Hermoine or Potter himself.
Hermoine or Ginny. I can't decide...
Cuthbert Binns...As my father always used to say, zzzzzz...
Longbottom, because his name is ridiculous translated to my language.
Ronald Weasley. His wand surprised me the most.
I both hated and loved Ronald Weasley.