A former work colleague used to (probably still does) have a part time job working for a pyrotechnics company doing professional displays.
During one display, one of the 6" mortars didn't fire properly - the primary charge that lifts the shell to x hundred feet fired correctly, but the secondary charge that explodes it didn't go off - he discovered this when it landed again about 6 feet away from him - apparently the hole in the ground was quite impressive.
The company that manufactured the pyro claimed that it wasn't possible for it to fail in this manner - he offered his underpants as evidence that it had
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