Perpetuum Mobile

"Gary's mod" is a modification of a video game engine to include some aspects of mechanics. By exploiting the fact that you can build a box of water with an open bottom where the water doesn't all pour out, the author of this video built a perptual motion machine in that game world.

In AI we often model our problems as "energy minimization." You can turn that around and say that nature solving an energy minimization problem is acting artificially intelligent.  That's why perpetual motion machines are interesting, even though they never work: no matter how clever we are, nature always figures out ways to make them not work consistent with the laws of physics. Nature always "outwits" us.