First off, let me say how disgusted I was when reading the book on discovering Scabbers was evil. There are so few positive role models for rats in the mainstream media, that we tend to clutch at straws. Even as poor a rat as Scabbers was to be admired, until we find out he is in the evil employ of He Who Must Not Be Named. I would however suggest that everyone keep an eye on that rat in the last book.
Also worth mentioning was Professor Lupin. A lot of subtlety and ambiguity surrounding this character was unfortunately cut to fit in the movie's time frame, but he looked gorgeous as a werewolf! Still scary and menacing, but also graceful and elegant, and he walked as comfortably on four legs as he does on two.
There's more I could say, but these were the two most important bits.