29. Christina Aguilera
Xtina kicked off the decade by flying her freak flag high for all the sweet blond pop starlets who just wanted to mud-wrestle and box with other chicks. Now, she's a 31-year-old MILF and The Voice judge who's newly single after divorcing her music-biz douchebag of a husband. But that four-octave vocal range? We could still make her hit the high notes.
DECADE ACHIEVEMENT: The "Dirrty" video. 'Nuff said.