In a year of personal ups and downs, Simpson, 25, has thrown herself into charity work for kids with Operation Smile—and, of course, kept flashing those famous teeth.
"I've always had the nickname Rabbit," says Simpson, who's never worn braces and considers the "buck" of her teeth one of her favorite features. "I can make the best bunny face. No one can stay mad at me when I do the bunny face." While she reserves her killer bunny face for special situations, it's her smile that lights up a room. "She has the best smile with a capital S," says designer Michael Kors. "Sporty, sexy, sensational."