Ben Chapman, a designer on the Thingiverse, has come up with this great looking knife sharpener.
The 3D printed sharpener works by fitting onto the bottom of a standard size ceramic coffee mug. Chapman, in a moment of genius, realized that the bottom of a coffee mug usually has a ring of exposed unglazed ceramic. The knife blade fits in a slot at the proper angle to hone the blade on the ceramic as it is pulled across it.
The protruding stand on the side allows the sharper to be used with the mug tipped at an angle and the blade moving vertically through the slot, or with the mug resting on its top lip, for sharpening at a more horizontal angle.
Awesome design, and inspired use of an existing household item to complete the sharpener. Now, maybe we can convince Mr. Chapman to get the design up on Shapeways?