I like devices where it's hard to figure out what they actually do, and the Octocube from French designer Vivien Muller is a fine example. Built entirely from 90 degree copper tubing elbows, the Octocube is actually a radiator for a hot water heating system. Within the 14 inch cube, there's enough copper tubing for it to actually become the radiating surface without any need for traditional radiator fins. The only thing that isn't clear is why it's called an Octocube, seeing as like all cubes it has six rather than eight sides.
For now the Octocube is only a design idea, and is not available commercially.