I think girls think I'm a sex offender. They get really nervous whenever they're alone with me. I can't really blame them, though, I'm 6'7" and it would be super easy.
Also, there seems to be a rather widespread epidemic of people who think "gay" and "abstinent" are the same thing. Really, I'm abstinent, and when people find out I always get that "OMG ur gae????!!!11" type statement. Not only is this annoying, but one time this one guy tried to "cure" me of my abstinence by trying to hook me up with some slut he knew. I had to threaten him with a restraining order to make him realize I was serious.
This one's not as pertinent as it is funny, but one time one of my friends asked me if I was Jewish, apparently on the grounds that I have a prominent Roman nose, curly dark-brown hair, and there was this one blond, blue-eyed girl in my class who hated me intensely for no apparent reason.