If you ever want to make friends with people at a bar, show them one of your scars. I did that once, and the guy next to me decided to show me one of his. Then someone else joined in. Pretty soon just about everyone there was rolling up their trouser-legs or sleeves and shirts to reveal theirs.
The stories about how people got their scars became far-fetched. I heard unlikely tales of shark attacks and rampaging bulls. It became a funny competition.