I have an unintentional reaction of glaring at people who stare at me. I have been trying to work on that. I've learned to remind myself that when people stare, the chances that they're thinking bad things about me are pretty low. People are like crows - they're attracted to shiny things. People stare at people who stand out; a lot of the time, they're staring because they're curious. People are staring because I'm interesting, not necessarily because they're judging me. I try to respond to staring with a friendly smile, because a lot of the time, people just want to know what's going on. Sometimes that person will come over and talk to me, and they turn out to be nice.
I guess I've dealt with more aggressive responses a few times, but it doesn't happen that often. If I think someone's going to try to corner me or something, I'l either get out as fast as I can, or go somewhere with a lot of people and wait for them to get bored and find another target.
If I overhear someone say something nasty about me, it can hurt. Sometimes I have to go somewhere and give myself time to recover. Sometimes I have the self confidence to just say something nice to myself to counter it, but not always. Sometimes all I can do is wait for myself to forget about it.