Casetify X Essential Skin
If you want a super thin iPhone X case the Casetify X Essential Skin is what you need. They claim this is the world's thinnest case and after using it on our iPhone 8 Plus it's definitely a claim that looks plausible. At 0.45mm thick, this case adds a little grip, a little change to the color and it's matte finish means you don't ned to worry about fingerprints and grease showing on the iPhone X's glass back.
There's a little lip that raises up around the camera lens to help protect it, but other than that, this is a super slim case. The matte finish is perfect with a little added grip and the case itself fits like a glove. This won't add protection from drops, but if you want to protect your iPhone from scratches and fingerprints it's the perfect options.
$25 from Casetify