Ugly women are sexier than pretty women
Save for the extreme (unless I'm very horny), I find ugly women more arousing than sexy women. It's part of the more naughty, animalistic side of my sexuality. Pretty women are great too, but the more horny I get the less disgusting and more arousing ugly women seem. I'm only guessing, but I think that most men (if not most people) are like this as well, whether they take advantage of this feeling or repress it.