Polaroid Cube was suggested by Landon Kryger. It is a hollow spherical 2x2x2 Rubik's Cube. However, instead of stickers, it uses polarizing filter. The object is to turn the puzzle and make all three directions opaque.
Watch the YouTube video
Read at the Shapeways Forum
Read more at the Twisty Puzzles Forum
Please contact Oskar directly if you are interested in obtaining a fully colored, stickered (uh, polaroided) and assembled sample of this puzzle.