It doesn't matter how great in power some armaments seem on paper - sometimes, stuff just happens and even the most ingenious devices end up relegated to the White Elephant chapter of history. Often times, these devices and machinery that never saw action get caught up in a political quagmire, or show up in the wrong place at the wrong time, like when there's no conflict.
Other times, in the greatest stroke of irony, some of the instruments and machines were just too great for their own good. Too big, too powerful, too expensive - or just too over-the-top to prove practical in battle. But no matter what ultimately kept them off of the field (including peace), it's hard for military hardware enthusiasts to not feel a little pang of regret at the idea of these machines winding up in mothballs.
Vote up the most innovative armaments that never saw action below.