My fiancé and I went to SakuraCon in Seattle in 2001, as Princess Serenity and Tuxedo Mask from Sailor Moon. No, that's not my real hair.
We went to SakuraCon again in 2004 and I dressed as Misty from Pokemon.
I've been to several other conventions dressed as the Fourth Doctor from Doctor Who.
I haven't decided what I'm going to be for this year's ComicCon in September. (Last year I went as Indiana Jones.) It'll depend on my mood and the weather. It's unpleasant wearing a heavy costume in hot temperatures.