One of my favourite gifts for Christmas this year was this "Ghost Cube" (on the left). After a bit of fiddling with it, I figured out how it works: Take a regular cube (like the one on the right), twist the two layers as shown, then stand it on its corner as shown. Then take an imaginary saw and cut the puzzle into the shape of a cube (to match the alignment of the Ghost Cube on the left). Then remove all of the colours so that you have no hints about what pieces go where.

This is a devious puzzle, and quite difficult to solve, especially since you can't twist some of the edges in the state where it looks solved, so nothing lines up exactly while you are actually solving the puzzle. I managed to solve it once, spending an estimated four hours over the course of several days. I think with some practice I could get my solve time down to less than an hour. Of course, the world record is a ridiculous 33.80 seconds. Unfortunately I don't have much time to practice these days.

Technical Details: These photos were taken with my Canon 5D Mark II + EF 70-300IS at 70mm, ISO 800, f/5.6 for 1/100th of a second.