I have seen a massive collection of ordinary items that have been modified to shoot ammunition, one of the coolest was an ordinary tire iron that fired a .22magnum.
I was amazed to see a rat-trap shotgun on display at the State Police training headquarters. So easy to make with a board, piece of pipe, roofing nail, and a trip string. Sometimes showing off trophies is not a smart idea as it educates your criminals!
Of course the super-soaker shotgun may have been a Darwin Award in the making!
I watched one video where the guy made a zip gun out of stuff in his shop in about a minute or two, then he disassembled it because he said it was illegal to own.