I've gone out with guys that have extremely narrow preference ranges. Typically, though, I find that most do have a type. I personally don't have that much of a 'type'. I do like muscles but as for other attributes like height, race, eye color, hair color (or even no hair), etc. have not been aspects that matter to me.
If I had to 'type' someone as what I would be attracted specifically to then it would have to do with personallity.
Something I have noticed though in the past as far as my friends are concerned is thier observances of others. If I pointed out some guy that I thought was hot and there was some attribute about them that they specifcally didn't like (i.e. brunette) then they would say that I like brunettes because that's what they would remember even if I had prevoiusly also pointed out someone who was blond or bald or redheaded. Later they'd be pointing out brunettes to me as if I'd only go for a brunette.
Now a six-pack, that will get me every time.