This is a list of things that is completely acceptable to on Halloween. Most of these should not be done any other day of the year.
Egg the houses of people handing out raisins. Those aren't candy. They are grapes that need to be thrown out.
Go to churches while wearing a devil costume. Play it completely straight.
Take a friends kid trick or treating. This is a loophole that lets adults get free candy.
Dress like a whore. That is pretty much what every female costume is anyway.
Use it as an excuse to show up at your job out of uniform. Just show up in your regular cloths and claim to be some character. Even the worst ballbuster of a boss won't call you on this.
Hide behind be "in character" while in your costume to get a pass on saying grossly inappropriate things. You know, if you don't have the balls at other times.
Minor acts of vandalism.