#2. The 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.
#1. War Elephants and Incendiary Pigs
The ancients didn't have access to tanks, amphibious or otherwise, but what they did have was elephants. And of course, human nature is such that as soon as people see a giant, lumbering beast, the only thing they're wondering is the best way to use it to murder other people.
"Oh yeah, that might work."
Elephants were used in warfare throughout the ancient world, most notably by the Persians, who captured them from India. The rationale was simple -- elephants are huge and intimidating, with tough hides that arrows just bounce off of, and spears attached to their faces. If you're an exotic foreign army, the best way to frighten the Roman legions is to remind them that giant monsters are on your side, and unfortunately for the enemy with their pansy-ass swords, you can't just bring a knife to an elephant fight.
But war elephants weren't just a relic of ancient times -- armies used them right up to the end of the 19th century, in part due to their ability to withstand gunfire, and as shown in this 1893 photograph of the Siamese army, they could be equipped with cannons. Let's see a horse do that.
If we'd spent all that F-35 money on war elephants, we can guarantee you it wouldn't have been a waste.
Unfortunately, elephants come with a rather serious design flaw -- despite their size, they're huge pussies, and when you spook them, they don't really care whether they're squishing the humans on one side of the conflict or the other. So although they might be able to shrug off the enemy's weapons, there's a better than good chance that your elephant is going to go into a fear-induced stomping rage among your own ranks if it gets shot enough times.
So yeah, maybe not the best place to build a tower.
The Greeks came up with a particularly novel (though horrifying to animal rights activists) way of exploiting this fact. According to them, the elephant's natural enemy was the pig, although cartoons always taught us that it was the mouse. When they were besieged by Macedonian armies with their war elephants, the Greeks took the obvious course and coated a bunch of pigs with tar, set them alight and set them loose among the invading forces. Then they just sat back with a box of cigars and watched the Macedonians getting stomped on by their own terrified elephants.
Historians are divided, but there's some evidence that ancient armies might have used rhinoceroses to combat elephants as well. One report from Portugal in 1513 describes rhinos as "the mortal enemy of the elephant," being sent in to attack elephants with their face horns. Kind of like in 300, although we're sorry to say that most academics don't regard that as a reliable historical source.
For more crackpot weapons, check out 7 WTF Military Weapons You Won't Believe They Actually Built and The 7 Most Stupidly Overpowered Hunting Weapons.