either harry atau snape! neither of them are my favorite characters but i think they're the two best ones because they have the best character development. anda see both of them as they grow up and fight their demons and become adults. it's really cool how anda get inside their heads through all the books/movies, anda see what makes them tick, what they're afraid, what their motivations are for everything they do. and that's why i think they're the best. ^^
I'm just gonna go with Snape, because of my on-going ridiculous crush on him. Actually, there are so many good characters in this series, and it is a shame that JKR couldn't delve into all of their back stories. But Snape. Definitely.
