3The 430-Foot-Long Vengeance Cannon
Alongside whatever else World War II was about (we forget), the whole affair was kind of one big dick-measuring contest. So it was in this spirit of overcompensation that the Nazis put together the 430-foot-long V-3 cannon -- the V, by the way, stands for "vengeance."
Bundesarchiv, Bild 146-1981-147-30A / CC-BY-SA
The Nazis were a subtle people.
This thing was capable of firing more than 300 shells the size of schoolchildren an hour, over a range of up to 100 miles. This way, they could literally shoot somebody from the next country over, which they did on the one occasion they actually got to use the thing, to bombard Luxembourg from Germany in 1945.
As it turns out, shooting bullets at a target 100 miles away is kind of difficult, and was more so in the 1940s. As indisputably badass as the vengeance cannon was, the bombardment of Luxembourg killed an estimated 10 people -- hardly the most memorable battle of the war, considering the effort and expense that something like this took to build.
You'd expect a rain of explosive dicks to do more damage.
On top of that, the sheer size meant that these things weren't exactly mobile, so any one that they actually managed to build was a sitting duck as soon as the enemy figured out where the bullets were coming from, which was simple enough for anyone who managed to pass grade school physics.
Even before they finished building them, the Nazis had a tough time keeping the V-3 cannons secret. When the Germans started building a bunch of them in France to aim at London, the British knew that something was up, and although they didn't know what the V-3 actually was, they nevertheless sent the air force in to bomb whatever it was into oblivion. And it's a good thing, too -- just imagine how many tens of people might have been killed.
Tens of tens, even.
2The Pants-Shittingly Loud Thunderscreech Propeller Jet
The F-84 Thunderjet is often considered the fastest propeller-powered aircraft of all time, capable of achieving almost the speed of sound, and that's an achievement all on its own. Generally speaking, the aviation industry has been trying to get away from the propeller for the same reason the automotive industry has been trying to get away from, well, horses. So it seemed a strange idea, after they had invented the modern fighter jet, for the U.S. Air Force to go ahead and throw a propeller on it.
"I've never met a problem that couldn't be solved by more propeller."
It made sense, though -- engine-powered jets were faster, but they took a hell of a long time to accelerate to top speed. Propeller planes had the acceleration advantage, so to get the best of both worlds, they equipped a jet with a propeller that spun at around Mach 1.18, just over the speed of sound itself. It was the most badass attempt ever made to improve on the Wright brothers' "spinny thing on the nose" idea.
While there's some dispute about whether the Thunderjet is really the fastest propeller aircraft ever made, there's no dispute that it was the loudest aircraft ever made. It turns out that a propeller spinning that fast has some unfortunate side effects -- the plane could easily be heard 20 miles away from the base, earning it the nickname "Thunderscreech."
Or "Holy shitting butthole, my ears are bleeding!"
But the inability to sneak up on communists wasn't the worst part. The perpetual sonic boom that this thing was broadcasting was so godawful that it actually triggered nausea, seizures and loosening of the bowels. In fact, the pants-soiling reaction that made the Thunderscreech notorious is the source of the "brown note" myth, the rumor that there's an actual frequency of sound that can make you poop yourself when you hear it.
Come to think of it, this would have made a pretty nifty weapon, if not for the risk of the guy in the pilot's seat getting a sudden case of the poop seizures.
The remaining Thunderscreech is used for CIA prank wars.