When I first got my Turbo on Halloween, the options were considerably fewer than now. It was also less clear that some cases didn't fit both BN and MG versions of the Turbo (all the Verizon cases fit both).
So, the first case I ordered was the black X version Cimo directly from China. It turned out was for the MG version and I have the BN Turbo. It didn't fit (sides are too short).
I bring it up because I was very impressed with the quality and look of the case. I don't like the S design Cimo, but the X was pretty cool, although I do prefer a plain black.
I would recommend it highly, especially since you want the thinnest. Note that I too had a Feather shell for my Droid Maxx and I hated it. I couldn't see the point of using it. I do like the slimmest I can find, though and have historically used a silicone skin of some sort as my main case.
Beyond that I have both a black Tudia and a red Diztronic and they're both very nice. They seem to me to be about as thin as you can get. Definitley less bulky than an Otterbox Commuter or even the Verizon glossy silicone case (I have one in black), for example.
My guess would be the thinnest/lightest would still be a silicone gel skin, but they seem to have gone away to a large extent.