My name is Rebecca, and my favorite Halloween costume was when I went as the Headless Horseman in grade school. I rigged my brother's football shoulder pads like a hat and got a long trench coat to button over the top of them, and carried my mom's wig stand around all day.
Other Halloween costumes of note from my childhood included: the classic witch, a flapper, an angel (recycling a holiday pageant look), and a lumberjack.
Since I've been a grown up I tend to go with things that are less obviously a costume, but instead me looking like a funhouse-mirror version of me. Like wearing my mom's LBD from the late 60's with the brunette bob wig she had bought at the time, which has made people shocked that I cut my hair or inspired at least one person to tell me I should dress like that all the time.
These days my standard Halloween costume is to dress punk/goth (continuing the me, but not quite me theme). I own a lot of black clothes and safety pins which I combine, and then do my makeup and hair in a way that is much too labor intensive for every day but is always a little bit tempting to maintain. I like the feeling of being just a half-step removed from my regular self for a day. Perhaps enough small steps will take me somewhere entirely new.
What is/was your favorite Halloween costume?