Not every building set has to be made from colourful plastic bricks. If you're looking for something a little more challenging — and rewarding — than Lego, Hermann Böhm has created this gorgeous stainless steel and brass Stirling engine kit that will take you about three satisfying hours to build. And of course it's fully functional once assembled.
The final product has a lovely retro-futuristic feel to it, and it sounds amazing when running. Since all a stirling engine needs to run is a source of heat, the pair of included burners will keep it humming along for up to 20 minutes at a time. You could even use the engine to power an over-the-top pencil sharpener if you wanted to try and write-off the $US310 kit as a business expense. Just don't tell the taxman where you got that suggestion. [Böhm Präzision via Werd]