Joule Thief

I Just had to post this, its a very clever little circuit (published by Z. Kaparnik) that helps you get whatever is left in battery out as useful energy.

Here is a video..

Stubblefield Electrical Battery

Daniel McFarland Cook 1871

In 1898, Stubblefield was issued U.S. Patent 600457 for an "Electric battery," which was an electrolytic coil of iron and insulated copper wire to be immersed in liquid or buried in the ground, where it could also serve as a ground terminal for wireless telephony.