99% of my projects are 10% done. :(

Probably the most pleasing project I have ever done. A fully "from-scratch" GPU voxel raycaster. Octree is 80% done, but I hit some limits on OpenCL debugging and my patience for C++ so I moved on to other things
I'm like, 1/8th of the way to creating yet another flappy bird clone. This time in Rust & Amethyst.
Conways game of life is very satisfying to implement on the GPU, especially when you can use buffer sharing between OpenCL/GL. The rendering & simulation happens completely in-core and on the same 2 swap/frame buffers. Adding coloring & fading also can make some neat designs
A cheap(ish) Tamiya bulldozer kit, 3D printer, 2 Arduinos + NRF24's and some stepper drivers makes one surprisingly fun little dozer. Controller was designed in KiCad and sent off to be manufactuered into a PCB
Calcuate the commute times to a central point using the HERE maps API! Fun story, before switching to HERE maps, I ran up an 800$ bill in 5 minutes using the Gmaps API.
My current long-term project, a 2d drawing machine using 2 stepper motors and a very temperamental pen holder. Image processing is done in Rust & Vulkan, but is currently stuck within Rust's current GUI hell.