Finally getting to participate, and doing so without looking at anyone else's list (so I'm sure I'm gonna forget some, and then slap my head and think, "HOW COULD I FORGET THAT COSTUME???").
Number 5: Killer Frost
designed, I believe, by Pat Broderick, and based on Asian deity crossed with a prom dress, this outfit SO should *not* work. .but it really, really does.
she looks like an Ice Carving at a wedding, which is just perfect for the character. Everything from the giant gown, to the head-piece pearls, to the way she was frequently drawn with "smoke" coming from her mouth when she spoke, to me this was an absolutely perfect design for this character.
it really saddened me when they changed it to make it more simplified in later years, and I despise what she's currently wearing in the JLA book.
but her original look? Perfect.
Grand Dictator for Life of the Classic Comics Christmas