In the olden days it was used to drain the colour out of the world, and make everyone walk too fast.
These days however, it is mainly used for Special Effects, used in such films as The Blair Witch Project.
In 600 BC it was discovered that rubbing a piece of amber with cat fur would cause it to attract small pieces of paper. This discovery led to the invention of the first apparatus for the mass production of static electricity, in which a number of cats are attached to the rim of a rotating wheel, aligned such that their fur comes into contact with a specially shaped block of amber.
Maintenance of the device proved to be almost impossible as any engineer attempting to remove the wheel from its mountings would be instantly lacerated by the sharp claws of the highly charged cats, so the 17th century German scientist Otto von Guericke improved on the design by replacing the cats with balls of sulphur.
By this time the uses for static electricity were growing in number and variety, and maintaining the supply of cats and sulphur presented great problems. A method of storing and transporting static electricity was clearly needed.
Early attempts to use cardboard boxes for this job proved unreliable and dangerous, as the electricity would leak from the bottom of the box and cause contamination of the ground. This proved especially problematic for sheep farmers as the escaped electricity would cause the sheeps' wool to stand on end. Any slight breeze would pick up the sheep and carry them for miles, much like a dandelion seed.
Enter the Dutch physicist Pieter van Musschenbroek who hit upon the revolutionary idea of storing the electricity in a bottle. This proved much more reliable because a simple cork could be used to prevent the electricity from spilling out. His invention was titled the Leyden jar because nobody could remember how to spell "van Musschenbroek".