I have rejected guys with small cocks before...mostly thin cocks. I really get skeeved out by the pencil dicks for some reason. If I'm cruising, or trying to hook up, I try to get the guy to show me what he has before we go any further so that I don't feel obligated to go further with someone I'm just not into.

It's really a shallow thing, but I say you like what you like and no one really can dispute you on that.