You need:
Fake blood
Fake skin
White T-shirt
Blue jeans
Put on the clothes and take the fake skin and smear it on your face. Now take the blood and make little lines. You can mold gun shots out of the skin too.
Thanks to an anonymous submitter for this gruesome idea!!
Another Idea
Hi my name is Jodi. Here's a great idea for a scary costume! First, paint your face white. Get fake scary skin, and apply a few layers on your face. Make holes in it with tooth-pick.
Put white, brown, and black face makeup in the holes. Make brownish red lines in the holes, and on your face. Then put fake blood on your face. You may want to make black rings around your eyes. Spray your hair black or white. then put on torn plain or fancy clothes.
You will be the scariest creature around!
Thanks to Jodi for this creepy idea!