The final "Jackass" movie is a glorified clip show with a few new bits for good measure, but it firmly cements the franchise as a vital piece of American history once and for all. Once upon a time, an aspiring actor who self-identified as Johnny Knoxville — birth name Philip John Clapp — decided to shoot himself in the chest with a .38-caliber revolver with nothing besides a cheap bulletproof vest and a short stack of porno magazines for protection. He pitched that vital scientific experiment