The Most Useless Machine Ever
instructables.com
instructables.com
My favorite was the "solar-powered nightlight", which was a solar panel wired directly to a lightbulb.
For some industries they can be quite useful.
The original has an uncanny hand which changes the character of the device from purely mechanical to somehow philosophical.
(Normally I'd dig up a link, but I don't have time right now.)
After seeing a video of such a machine I just had to have one of my own. Normal 0 According to Wikipedia, Claude E. Shannon built the first “Ultimate Machine” based on an idea by Marvin Minsky.
http://www.kk.org/thetechnium/archives/2008/03/the_unspeakab...
Ford Prefect: Don't.
Arthur Dent: [presses it] Oh.
Ford Prefect: What happened?
Arthur Dent: A sign lit up saying "Please do not press this button again."
To me, it looks like the machine is bothered when the user flips the switch and wants to be left alone. Of course, that's ridiculous, but that's the fun of the machine.
A simpler alternative would have a STSP switch with a battery and motor. When you turn the switch on the motor raises the arm and switches itself off, a weight on the arm could lower it. Then again my version wouldn't work in zero gravity.
http://www.andrewlipson.com/lego.htm
This is the same Lipson as in the Lipson-Shiu Corporate Type Test
Fortunately this machine seems to be immune against that.
Now if they made a variety that turned itself on, that would be something.