Maybe it's just me, but I think Gwen Stefani is pretty hot-looking and doable in the "Just a Girl" video, whereas everywhere else, she doesn't look quite as attractive. Don't get me wrong. She's cute, but that video really does it for me for some reason.
I don't have a list myself, but I've always had a bit of a thing for Nancy Wilson (who must be approaching 80 by now), and the two skinny Wilson Phillip singers.
From a strictly metal standpoint, I'm more into the Lita Ford/Janet Gardner look instead of the Joan Jett look.
From a strictly non-metal standpoint, I'll go for Shania Twain, Faith Hill, Chely Wright, Sara Evans, and a handful of other Country singers. I'll also throw in Christina Aguilera and the Corr sisters... especially Andrea.
I know I'm missing a few others I can't think of at the moment.