
How about the discussion of the STS Tether experiment.  Ran forward,
it would suck energy from the Earth's magnetic field, while trivially
slowing the Shuttle.  It could also have run backward -- if they ran 
electricity through the tether the other way, it would have trivially
propelled the Shuttle faster.

But an even better example comes to mind.  There's this electronics guy,
someone like Craig Anderton or Don Lancaster.  Ten years ago he wrote about
an invention of his.  He could take a light-detector, run current through
it at about a hundred times its rating, and it would glow.  He got legal
rights to this design of a combination "fiber optic emitter/receiver".  This
turned out to be the basic unit of ATT's  (I think) plan to bring Brazil's
communications system into the 21st century.  (The article was mostly about
his legal wranglings with the company that eventually got him well-compensated
for his invention.)