SAOIRSE RONAN, 16
Doesn't ruin: Atonement (2007), The Lovely Bones (2009)
Why they don't suck: Irish-American Ronan earned acclaim and an Academy Award nomination for "Best Supporting Actress" with Atonement, playing Briony Tallis, a 13-year-old who has her older sister's lover sent away for rape because she secretly crushes on him. Child's play? Not her thing.
Child version of: Cate Blanchett