A two-part snap-together case for the Raspberry Pi 2 (probably works also for the model B+). The two part design is intended to be printed with minimal support structures and to be tolerant to warping when printing with ABS. To make the case fit even if the front and back sides are slightly warped the back part has two slots for the edges of the Raspi's board that allow the board to fit in even if the case edges are warped. If you don't need that you can modify the corresponding Tinkercad file.

Front: https://tinkercad.com/things/jsU2tWXlk45
Back: https://tinkercad.com/things/faPvYSBrbJI

Disclaimer: use this case at your own risk.

Just print the back and front parts upright with the opening at the top as they are in the STL files. A raft is not necessary but can be helpful to reduce warping. When printed remove the few support structures and clean the edges of the openings if necessary.

To assemble I recommend that the Raspi is first inserted in the front so that the network and USB connectors fit into their respective openings. Then the back part of the case should be pushed over the back of the Raspi while slightly pressing the back case to make it a bit wider so that it will fit over the micro USB and HDMI connectors. Make sure that the Raspi board fits into the the holding slots in the lower case corners. The case part should fit firmly together if printed correctly.

For the example print shown in the images I've used an Up! mini with white ABS. The Up! mini tends to print ABS warped as can be seen from the example. The case still fits the Rasperry because of the slots at the case back. The black one is printed with PLA without any warping and also fits well. I would be interested in experiences with other printers and/or materials.