Incipio Galaxy S8 Case ($19)
Incipio is a popular name when it comes to cases. A big part of that is because most carriers sell their cases in stores. The company has over 15 cases for the Galaxy S8 or S8+.
My favorite is the Incipio Carnaby series. It's a durable yet flexible TPU case with a nice metal strip 3/4 of the way to the bottom of the back of the phone. The best part though is the real cotton materials used. It makes it very comfortable to hold and use, and you won't accidentally drop it. It's hard to explain but it looks and feels like denim jeans.