You could say, "Grow up," or "And insulting me makes you feel special, how?" or you could just roll your eyes, give him (or her) a disgusted look and walk away. Myself I usually say "Did you intend...
Its really not that hard unless your a stuck up brat but you just look at the person and find something in there features that you think is pretty. But you don't only have to say something nice about...
If you want to do it nicely this is what you do. First you tell them to get out of your face and say i don't like it when you do that. So don't do it. But my way is to say, Get out of my face, i...