Geary Cube is a Rubik's Cube with gears inside. This way, opposite sides always turn in opposite direction.
As a result, the cube always displays nice symmetrical patterns. Although easier than the original Rubik's Cube, it will still take quite some thinking to solve this one. Transparent objet is the material of choice for this puzzle, so you can see the gears inside. The puzzle is an idea of Bram Cohen, worked out in 3D by Oskar van Deventer. See this YouTube clip. The prototype on the photos was made by George Miller, using a combination of white FDM and transparent object, the latter from Shapeways.