I just came across this little piece of machinery while browsing the Makezine.com website:http://en.wikipedia.org/wiki/Geneva_wheel
By having two "overlapping" wheels and some geometry trickery, you essentially have a very tight gear(?) with a very distinct ratio. For every 360* turn of the primary gear, the secondary turns by 60 degrees (or 90 degrees, depending on how you cut the channels). I think that 90* is the largest rotation you can have.
The mechanism feels like the internal workings of the Master Lock "Speed Dial".
I've posted this in TOSL on the idea that having such a tight mechanism could be beneficial in improving dial/combination locks. Or maybe it could be applied to a lever lock, somehow.