What is your choice for the best film costume ever worn? [View All]

What would you consider to be the best film costume ever worn? I am thinking of one of those scene or, better, film-stealing pieces that creates its own visual dimension in the film -- a costume or outfit that once worn, changes our sense of the character and his/her fate forever.

My choices:

1. Keira Knightley's green silk backless 1930s-era gown in Atonement
2. Ilsa's white suit in Casablanca
3. Scarlett's "curtain dress" in Gone with the Wind
4. Darth Vader's entire all-black ensemble, worn when we first behold him on screen in the original Star Wars (very GenX of me)

My top choice is Keira Knightley's green dress in Atonement. That dress just had this perfect quality -- the vibrant shade of brilliant green, worn by a beautiful actress at precisely the right moment in the film -- a crucial turning point when love and tragedy meet and merge (ah, James McAvoy as the tragic Robbie Turner...when he first catches sight of Keira (as Cecilia) in that gorgeous frock...).



Apologies -- I am too illiterate technologically to post a pic, so here is a link to a good image of Knightley in the dress, without her smoking. If anyone else can post the pic, I would greatly appreciate it!Thanks to everyone for your ideas.