I've had to think about this for a while. I think I'll have to include some runners-up. I decided to go with the character that with whom I have the most emotional attachment.
In the end, I consistently love Blair Waldorf.
First of all, she has the most amazing wardrobe EVER. Second, I always want her to be happy, I want her to succeed--even when she's doing things she shouldn't be doing. When her heart breaks, so does mine.
Runner-ups include:
Starbuck--even though she annoys the shit out of my for so long.
Adelle--I think she's an amazing woman.