Arthur Sacek built this milling machine (a tool for carving and cutting solid materials) entirely out of Lego pieces–minus the main carving drill. It takes a computer rendering of an object and carves that rendering exactly in full 3D onto a piece of floral foam.
The machine uses a Mindstorm NXT kit, and works on a CNC design not too disimilar to Pancake Bot. Once the drilling is done, it may seem as though nothing has happened to the block of foam, but dust (or, as the video suggests, vacuum) off the shavings and you are left with a very accurate 3D object.
Not bad at all for a Lego machine, and it could come in pretty handy–forget a birthday? Give a 3D caricature. In fact, it could be useful for any occasion when you’re trying to come up with a geeky and quirky present. Look at the video below to see a face carved out of the foam: