A friend of mine went as a generic baseball player one year.
He was on the school's team.
EDIT: To own up where I've been cheap too, I went as
Three Hole Punch Jim one year. Yeah, I know copying a fictional character who's being portrayed by the writers as not even trying is the bottom of the barrel, but in my defense, it was hard to find something that fit the dress code at work, which—despite their encouraging us to dress up—we were not allowed to break. (Dress code was button down black or white shirt, black dress pants, no colors of any kind. So glad to be out of retail. :p)