1. Emma Roberts - American Horror Story
FXEmma Roberts transitioned from child star to adult actress in the blink of an eye. One minute, she's Julia Roberts' adorable niece, getting her big break on Nickelodeon. She's playing Nancy Drew and Addie on Unfabulous, just generally really wholesome stuff. As she developed into her late teens, you could start to see a genuine desire on her part for more significant dramatic material, and she made a number of appearances in small independent features. But as it stands right now, American Horror Story is her grown-up acting calling card, and one that any actress would be proud of. In the most recent season of the popular FX horror anthology, Roberts played Madison Montgomery, a young actress who discovers that she is a witch and is sent to the Academy. She has a particularly dramatic arc on the show, which begins with a graphic rape scene, takes a brief pit stop with Carrie-like powers of telekinesis, and ends with the untoward zombie sex. Morally quandaries abound, and while it's clear that American Horror Story is doing its best to push the envelope, the one thing we all walk away from the show with is the fact that the little girl from Nickelodeon is not such a little girl anymore.