Cloaca Professional by Wim Delvoye
This is a machine which digests food, and produces poo. The museum staff feed it real food from the restaurant and cafe on site. I was fortunate enough to be passing at feeding time, and got to see him eat his dinner. (The female staff member conducting the feeding explained that it had to be a male, because a girl could never smell that bad…)
The feeding involved an explanation of what he was eating, which was basically shameless cross-promotion of the eateries (and Moorilla's Moo Brew), but quite charmingly done. They use two small capsules of enzymes with each feed, but otherwise the machine does all of the digestion.
The machine itself is quite beautiful (if you're into industrial design) and I just love the concept. It's geek art.
This should be required viewing for every high-school student in the state.