My favorite would have to be Luna Lovegood, because everyone always underestimates and misunderstands her. Every time she's in a 'scene,' I can't help but love her. And the way she talks is so strange, but extremely appealing to me. Before Luna came into the plot, though, I always liked Snape. His presence seems very intimidating and mean in the books, but he was ALWAYS impressive and in charge. Also, you've got to love his wit. He's just all around awesome.