I love Snape so far (I'm almost done with the third book). Mainly for lines such as this:

"What would your head have been doing in Hogsmeade, Potter? Your head is not allowed in Hogsmeade. No part of your body has permission to be in Hogsmeade."

I read that part in the breakroom at work today and burst out laughing. I also really like Ron a lot. He's much better in the books than in the movies. He seems a lot more sure of himself and confident in the books. Right now, i'd have to say Hermione is my least favorite. But I just don't think a lot has been done with her character yet.