I'm thinking about Halloween critters I'd like to be, not for Halloween, but for real, and I think Ghost takes the prize, especially if I get to haunt a theatre, a museum or a Victorian Mansion. If I had to haunt a grocery store or something, though, that would suck.
A vampire could be fun, although I prefer comic-relief vampires like The Count from Sesame Street or Count Chocula to scary or goth vampires.
Chainsaw killers? Although deranged hill folk hold an undying fascination for me, the last thing I wanna do is join their ranks. I like my Halloween characters defanged, as it were.
Mad scientist? Why not? Castle on a hill, messed-up hair, cackling and screwing with nature. Of course mad businesspeople turn out to be the real problem; mad scientists can only get anywhere with $$$.