My most useful personal project is my 3D printed phone case. The case is made of TPU and PLA.

 I started this project when I got a new phone and was not satisfied with the phone case options. I designed this phone cases with 3 functions in mind. Magnetic attachment compatibility, kickstand, and finger strap. I wanted all of these features while still keeping the case as thin as possible. The decals on the back of the cases are made using 3D printing toner transfer.