Emmett's geared cube, with a hand crank.
Video of pre-lubricated just off the printer version is here: https://www.youtube.com/watch?v=jfh5DNGP8tw.
Printed in PLA on a Makerbot Replicator 2 using Makerware 188.8.131.52 "Standard" settings.
A video of the heart version test fit is here: https://www.youtube.com/watch?v=o8CkCe5A-1w. Your cube pieces should all spin on their respective pins as easy as this before assembly. If not, follow this procedure: http://www.thingiverse.com/thing:271612/[hashtag instructions].
Print emmett's "CubeGears2-3.stl". If you can edit the file, you can delete one of the large corners, the center hub, and one pin before printing as these parts are not used. Clean up any stray filament in the gear holes. See Geared Heart, Motorized Edition (http://www.thingiverse.com/thing:271612) for the steps I performed in loosening up the geared cube as the it must spin freely.
Print all parts. While printing "Top.stl", I paused the printer at 4.2mm and changed filament from black to silver.
Test fit, file, sand, etc. for smooth operation. Lubricate the gears, "Gear Wheel Hand.stl" bushing surface and "Wheel Hand.stl" bushing surface using white lithium grease or petroleum jelly before final assembly.