This is another one of those impossible shape illusions. As usual, it can appear as a hexagon or cube. impossible hexagon cube Impossible Hexagon Cube
This is an old design but it was cool so I redrew it in inkscape. Read about it here. http://en.wikipedia.org/wiki/Penrose_triangle penrose triangle red Penrose Triangle RGB
An example of a necker cube and an Impossible cube (one arm runs across the other but is still straight, which can't happen in 3D; it's an optical illusion). cube necker cube optical illusion Necker cube and impossible cube
Three gears in an impossible (or at least immovable) arrangement. Done in Inkscape. gear colour cartoon Impossible gears