Cop
There are going to be a ton of cops out on Halloween. Illegal activity is as much of a Halloween tradition as trick or treating or egging and TPing your crotchety neighbor's yard. So people are going to steer clear of you because they think you're part of the po-po, or they're going to mistake a cop for a guy going as a cop. Also, don't wear any kind of costume that male strippers wear for bachelorette parties.
[Photo via @nypd]