Uploaded on Jul 1, 2011
Most people probably like Pistons because they allow them to build hidden doors and traps.
I like them because they revolutionize redstone circuitry.
(Please note that I didn't try to find out if anyone has already build something similar beforehand, so it might be possible that what I'm showing is nothing new)
World and schematics:
Forever A Troll from the Minecraft Forums posted this usefull list:
pTransistor - Tristate buffer(functioning like an AND gate)
ipTransistor - Inverted tristate buffer(functioning like an IMPLIES gate)
pPulser - Clock generator.
cTransistor - 2-to-1 multiplexer.
pcoPulser - Clock generator(with an inverted output as well).
4ppPulser - Quadruple clock generator.
pBMemory - A very crappy punched card reader.
PBM Array - A VERY EPIC punched card reader!