13. Reese Witherspoon, 'Walk the Line'
"Stand By Your Man" was a Tammy Wynette song, but it could have just as easily applied to Walk the Line's June Carter, who loved Johnny Cash but feared what his drinking and restlessness might bring to her life. Reese Witherspoon embodies those mixed emotions in this biopic that doubles as a romantic drama, and she does it with a no-bullshit frankness that keeps Joaquin Phoenix's Cash on his toes. Like several of the Best Actress winners on this list, Witherspoon has been stronger and subtler in other roles, but Walk the Line provided her sassy, down-to-earth persona with its most award-worthy platform.