One of the more bizarre weapons in military history was the Great Panjandrum, a huge rocket-powered spinning wheel of explosives designed to take out Nazi defenses along the Atlantic in WWII.
This is how it worked.
The Great Panjandrum was an attempted solution to a problem faced by the British in the early 1940s. The Nazis had built up ten foot high and seven foot thick fortifications along the Atlantic coast. The fantastically-named British Directorate of Miscellaneous Weapons Development (DMWD) was having trouble figuring out how to blow a hole through these defenses big enough for a British tank to get through. Since anyone running up the beach to deliver an explosive would never make it to the wall, the DMWD decided they needed some kind of explosive that could be launched by a landing craft in the water.
Their solution was to take two wheels, fix them together in the middle with a barrel full of explosives (up to 4,000 pounds), and power the thing with rockets strapped along the wheels.
It's the kind of wonderfully free thinking you would expect out of a fourth grader.
Here you can see the Great Panjandrum in one of its tests, chasing a dog as some kind of flame-spitting wheel of terror. The rockets rarely stayed attached to the wheels of the Panjandrum, often shooting into the ocean or over the heads of specatators, as well as causing the vehicle to careen wildly off course. The test Panjandrums, named after a nonsense line by Samuel Foote, never had a live payload, at least.
Unsurprisingly, a spinning wheel powered by around 70 rockets was not a successful explosives delivery device, often veering off course and falling over during testing. On its final test, the Great Panjandrum flipped onto its side and speared right towards a group of observing top-level officers, shooting rockets in all directions. The officers ran for their lives or dove for cover. While no one got hurt, the Great Panjandrum project was scrapped.
In 2009, a replica ran in a 65th Anniversary of D-Day celebration, going all of 50 feet without even trying kill a single person. As you can see, it finally got a moment of glory, remaining a military history oddity and never a weapon of destruction.
(Hat tip to Steve S!)