<a href="http://www.nerd-gold.de/">Roman</a> told us about <a href="http://www.toothycat.net/~hologram/Turing/">a turing machine in Magic: The Gathering™</a>. The design seems very complicated at first, I would have thought that there was an easier way to do it. However, with the 8 minutes invested so far, I did not come up with a better implementation.