Even if you've never actually read/watched Haruhi it's virtually impossible to ignore the massive amount of yellow headbands and the number of people dancing. Basically, you know the entire main cast of Haruhi yet without even having to see the series. So, who's your favorite Haruhi character? The titular Haruhi, Mikuru, Yuki, Kyon, Itsuki, or some other person? My favorite is probably Kyon. The commentary he provides throughout the series is the best part. He's also a mysterious character: what is he doing in an group of supernatural folk when he's only a normal person? Actually, I cheated and read a fanfiction that explained that part but he's still interesting!
So, list your favorite. But if you pick Mikuru I will have to shoot you.