I am small, skinny, and a quiet person. I'm a natural target for this type of shit. A while back on the way to my car someone called me a pussy with a group of his friends around. I told him to come over to my car and that i wanted to tell him something (people always get group mentality around others so i wanted to separate him.) I just looked at him and told him to never talk like that to me ever again. He looked shocked and uncomfortable. never did it again. Just confront them, they don't expect you to retaliate so when you do it'll shock them and they'll just fuck off. you're retaliation doesn't have to be witty, or even threatening in any way, you just have to do it.