I use my 5S mostly naked but I have a Caudabe Veil that I use occasionally when I know I'm going to be somewhere where I may need to put my phone on unfavorable surfaces.
It's really thin, almost like it isn't even there.
I have this on my 5s as well, and absolutely love it. I'm not a huge fan of cases, so I normally put a thin one on there anyway for minimal protection.
The Caudabe is basically feels like there is not even a case on the phone, but at least if I put it down on an unfavorable surface such as on a bar, the back of my phone isn't going to get all sticky.