A simple, and I think elegant, business card case. Customizer options allow for various shapes and sizes. For full customization, download the OpenScad script and template DXF file, edit the DXF (I use Inkscape) and go as wild as you want.
I've had best results at 0.2mm layer height, 2 shells, 10% infill. Standing upright and aligned on an axis with limited wobble, printed on a raft.