I don't know if I can think of a particularly sexy music video, but I will say that Hype Williams is one of the few video directors who can successfully make "music video girls" attractive. He particularly succeeds at this in Aaliyah's "Rock the Boat."
Also, that Chris Cunningham beautifully lampoons the very idea of those girls in "Windowlicker," which, while NOT particularly sexy, is in my opinion the best music video ever.
That said, if I were gay, I'd probably say "Untitled (How Does It Feel)" by D'Angelo was the sexiest video. And even though I'm not, I still think it's way up there on the list.
I don't know what I'd say is the sexiEST though.