Rubber-suited assailant or nun ("American Horror Story") Level of difficulty: For men, hard (and tight); for women, medium
"American Horror Story" has a variety of costumes to choose from for both genders, but if you don't want to hire a monster-movie makeup guy for a single night of dress-up, these are your best bets for keeping it simple. Not that a shiny latex unitard is the easiest sell for you men out there; it's skin-tight, the hooded head is going to make it hard to breathe (or eat candy), and it's probably going to cost you a pretty penny. (Your best bet for finding such a suit: your local Babeland or other "adult toy" store.) On the other hand, we'd have to admire your cojones (…literally; like we said, "skin-tight") for busting out in a bodysuit.
Women have it easier: a Sister Jude nun outfit is a commitment, but it's nice and loose, most costume stores will have one, and you won't really have to worry about hair or makeup. Throw a big crucifix over the whole thing, and you're done. (Rehearsing a convincing Bahston accent beforehand will really wow them.)
TV-Inspired Halloween Costumes
Click through this slideshow for the coolest costume ideas straight from the small screen.