I'm just curious as to why you like (or don't) certain characters, and who seems to be the most popular. No bashing other people for their character(s), and be nice!
For me I'll always feel Snape was one of the most intriguing, if not the most awesome characters.
Even though he came off as a very big jerk the events of the book tell us that's he's actually better than we gave him credit for (it takes a huge amount of courage to play a double agent when your boss can AK you whenever if he's unhappy).
A close second would be Sirius.
He spent ages in Azkaban for something he didn't do, and even after escaping was still a wanted criminal. But that didn't stop him from turning up in the MoM to help, but it didn't end well...
I don't like Umbridge, because she's horrible and she knows it.
She believes in punishments (blood quill?), and because of her position

she can get away with a lot of things.
If that's not convincing enough, she wears too much pink for anyone's good. I think my eyes are still watering.