oh, i have a cool idea for a scary costume!!!!! (you'd have to kinda make it yourself.......)
anyways, buy a white lab coat (they probably have a mad lab guy suit at party city)
rip parts of the lab coat, and paint red paint in spots so it looks like blood.
at party city, they have these awesome kits that sell things that look like cuts and eyeballs that have been pierced by glass, and you can stick the eye over your real eye, and put the bloody wound on your cheek, arm, or any place you desire................. wish i could find a pic, but i can't right now, so you'll have to believe me on how freaky/cool the cuts look........
or for a simpler look, you can buy a mannequin head (my mom just asked for one at party city and got it for $2), and put a hat, sunglasses, and/or makeup on it, and attach it to the shoulder of an oversized sweatshirt close to theneck. then you can stuff the sweatshirt with newspapers or pillows, and then put the sweatshirt on. you'll look like a two headed monster
yeah, i know my costumes require you to make stuff, but that's what i enjoy doing.................. or you can just got to party city and buy one of those bloody, gory costumes...............