How to handle unwanted flirting from a guy?

I honestly think the guy should take a freaking hint. But it's going to come to the point when your going to have to point out black from white and just plain out say, "I'm sorry but I'm honestly not interested in that kind of relationship with him." it doesn't have to be those words exactly but i think you get my point. But just let him know, if he had any respect for you he would back off once you said that. If he keeps trying, the boy is mental