A customer that doesn't want to spend any money. I live in a town where everybody in it thinks if they've spent 20 bucks, they've spent a lot of money. People like that will be glad to let you bust your tail all day to make 5 dollars. Get rid of 'em. You've got better things to do. These people burn me up. That's my attitude about them.
Learn to spot the pattern. People like that will never be satisfied no matter what you do.