Interesting question. It's definitely something more on the minds of a woman than a man, as demonstrated by Lola asking the question.
Personally, there are a few optimal situations. Naked is always acceptable, though I voted BDSM. I'm a fan of latex because it feels nice to the touch, but I would never be attracted to a woman wearing a leather mask with a zipper mouth.

I really like stockings and heels, and I'm a big fan of animal prints on nightgowns.
Halloween costume shops are full of sexy costumes. Too bad those kinds of costumes don't fit on my wife.

But along the same theme, I'm a D&D nerd (if you didn't recognize my avatar, you wouldn't understand

) so I would LOVE

to be with a girl wearing elf ears. I don't think it's rational, but it's hot to me.