We mentioned this on the podcast yesterday, and it's well worth a look. People's capability with an on-off switch is utterly terrifying, and this creation from the Redstone Development Foundation (brilliant name) is the most impressive I've seen. Before Minecraft, creator Markus 'Notch' Perrson made a game for a Ludam Dare competition called Prelude Of The Chambered, a super-simplified Dungeon Master-style first-person game. And the RDF, and one Berick Cook, have recreated a wire-frame version of it in Minecraft. Which is meta, as well as bloody impressive.
The RDF have previously brought us an 8x8x12 3D printer, an ASCII word processor, and a sync 4-bit to 7-seg dec decoder, which is, in fact, a digital number display. But oh my goodness, getting a game running in Minecraft? That's frightening. You can see it below: