Trees are useful for many things: providing shade, improving the look of the landscape, being a perfect base for tree houses and tire swings, and more. However, if the tree in question is ever cut or knocked down for any reason, you could be left with nothing but an unlovely stump in its place.
Position an unplated copper nail at the base of the tree stump, near the roots.
Pound the nail in as far as you can (preferably all the way to the head).
Cover the base of the tree stump, near the ground, with as many pounded-in copper nails as you can to hasten the destruction of the stump.
Test the stump for deterioration every few days after pounding in the nails. The wood should start to dry out and then rot.