I'm probably the only person in the world to say Percy Weasley.
I would love to know your reason(s).
Really? Honestly, I've just always liked his character - even with the events in latter books. The second time I read through the books I actually thought about why he left and I realized that I totally understood, and that I would do the same thing. I know that if I was treated that way by my family - and I'm not placing all blame away from Percy here - I'd leave too. It was clear to me that his ambitions weren't respected and I thought that Arthur should have been a little more sly about his suspicious on just why Percy got his shiny new job.
Other than that, I like somebody who is willing to do most anything to get what they want - but, of course, has some sense and limits. I like that he is smart and hard-working and doesn't blindly trust authority*. (I'm referencing HPPS here, when Harry and him talked during the feast.) He's also the only Weasley I really like and the only one I strongly identify with. Red hair and glasses is also nice.
*I think Percy was smart enough to realize that Harry was right but also smart enough to keep his mouth shut about it. I think it was about self-preservation and I'd have done the same.