A level-4 Menger's sponge.

A Menger's sponge is a fractal body with infinite surface and zero volume built by dividing a cube into twenty seven smaller cubes and removing the cross formed by the inner cubes, repeating this process ad infinitum.

In this image the original cube has been subdivided four times.

More info:

http://en.wikipedia.org/wiki/Menger_sponge

Available in two simple materials: A solid one and a translucent one. There are so many faces that the translucent one looks like a smoke-filled cube if you don't zoom in.