Shapewear - We hide it under our clothes, but now-a-days most of it is pretty, well, SEXY! It's one of our favorite pieces to photograph women in, because there are so many interesting and pretty styles. Shapewear also helps conceal some of the little problem areas we want to hide, smooths out lines, and gives us a little boost when needed.
Check out this article for The Lingerie Addict to learn more about shapewear and a guide to what works best on different body types.
Some of my favorites:
Assets by Sara Blakely (same designer as Spanx)