Although this thread is made of useful and awesome, I have a suggestion that's simple and might work. Breath loudly and heavily. It makes you look like a freak. For best effects, don't brush your teeth before you go out. Or belch in public. Farting crosses the line, but belching is considered a workable solution in this area.

Failing all of this, stare at people, that always makes them look away, I should know, lolololol