Mostly LEGO....
Often reverse engineered...
Always fun.
Dynamic LEGO:
Textiles: loom and braiding machine
A Walker
Claw Machine
Touch screen toucher; Etch-a-Sketch
Jenga Gun
Static LEGO:
Gothic Architecture
Dinosaur Skulls
Software / Hardware:
Pirates! reverse engineering
Special Relativity
Perceptron
For LEGO projects, I've included .ldr files. I use Bricksmith to create these. The ability to document a LEGO creation is so valuable - it's like adding save-and-restore capability.