I don't know if this one has already been mentioned but since I was involved in it I figured What The H---. The .451 Detonics Magnum!!! It came into this World after the Boss's kid ran a finish reamer in too deep. The result was a slightly longer .45ACP which could only be used with the shorter Remington 185gr. HP bullets. I custom built the first 100 cases using .308 Winchester brass. They talked somebody into building Factory ammunition for it but with Detonics being the only builder of the guns it didn't last long. Before long Detonics went out of business.