I think that there are different types of sexy. There is 'real-life' sexy and eye-candy sexy. One is the person I'd want to spend time with and the other one I'd just want to ogle for awhile.
I could make a list, but it would be pretty generic and invalid. Why? Because I don't know what makes a person sexy to me. I don't know if it's chemistry or if there is something in the whole pheromones thing. I just know that I've been attracted to a lot of different types of guys. Short, tall, red head, brunette, blonde, hippie, pothead, construction worker, military, asshole...find a connection in that and you have what I find sexy. If you find it, let me know, the only one I can see is that they are all men.
For eye-candy, I like toned, dark, and a Mediterranean-relaxed look. It's hard to describe, but I know it when I see it.
Beauty, or in this case sexiness, is in the eye of the beholder. But I will say that I enjoy being around people that make me laugh. I wouldn't consider that a sexy trait though. Just a trait that makes me want to spend time with a person. Sex can't happen 24/7, there has to be some personality to fill-in the gaps.
Wait, one trait that is sexy on everyone: self-confidence (not to be mistaken for arrogance).