My knee-jerk response would be the Red Head from Pirates of the Carribean, for obvious reasons.
I also really miss Henry from Country Bears, and Sam the Eagle from America Sings. These were two of my favorite attractions, and sadly there's nothing else like them left. I guess then I'd have to put Buff, Melvin, and Max as three of my favorites, as they are still visible, hiding in the Winnie the Pooh ride. They're still a reminder of that location's glory days.