This is by far the best way to get back on your cheating girlfriend: leave her with a mark on her back that she will remember forever. There's actually a very interesting guy who did this. He goes by the name of Ryan L. Fitzjerald, a tattoo artist from Dayton, Ohio, who had the unfortunate luck to find that his girlfriend cheated on him and decided to pay her back in a most original way: he gave her the worst tattoo one can have - poop!

(Note: this story was reported as being a hoax)