10. Rachel McAdams
Rachel McAdams' smile alone puts her on this list. Heck, with that smile she could play the Joker. But it's not just her smile that earns her a place, it's that she's become a very reliable actress over the course of her career, giving solid performances in a variety of roles, from mean girl Regina George, to Southern Belle Allie Hamilton in The Notebook, to perky reporter Becky Fuller in Morning Glory. McAdams has shown her versatility as an actress and I think the time is right for McAdams to explore a little more of her dark side and see what she finds- particularly since she recently took on a edgier role in Brian DePalma's latest thriller, Passion. McAdams also has the intelligence and poise to play Harleen before she becomes Harley, if the filmmakers decide to delve in to her back story.