The first time I got stoned it was off a bong made from the lung respirator of our weed hookup's best friend who had recently died. He mentioned how he was working on a gravity bong made from a missile fuselage retrieved from the military testing grounds. The idea was to fill the chamber with smoke and drop a bowling ball from the top and it would force the smoke out a tube and into your lungs. My favorite bong was this little tiny one I had made from a mini Pepsi bottle. I left it back in Washington State with a friend before I drove back up to Alaska after college.