
Sure, Leonardo da Vinci created some great art or whatever, and some cool inventions that make life easier. We also found out he was a weapons developer and he designed some badass military devices.
Then we took a closer look at those designs and realized da Vinci's a lot less artist and a whole lot more Darth Vader.
#9.
Underwater Warfare

- Leonardo da Vinci
Da Vinci's Design:

But what good is a submersible ship-cleaver without a SEAL team to rig charges?
That's right. Da Vinci designed his own SEAL team.
Why it Would Have Worked:
The Crusades turned city-states like Venice and Genoa into superpowers thanks to the usefulness of their mighty navies. If anybody was going to stand a chance against these two powers, they needed men like da Vinci to sink their fleets swiftly and silently. Underwater warfare would have turned every drop of water in the Mediterranean into a war zone that no ship would be safe in unless they had pledged allegiance to your kingdom. Your fleet would have been as feared as Poseidon himself.

Seriously, could this possibly be any more pimp?

Like this, only with more explosions.

A Robot Army

- Niccolo Machiavelli, The Discourses
As Cracked has examined earlier, many "modern" technologies are actually way older than you might think. Take the robot: invented by the forever badass Hero of Alexandria, and perfected as a killing-machine by Leonardo da Vinci during humanity's rendezvous with antiquity.
Da Vinci's Design:

A decoy worthy of Total Recall... until it's set for "murder death kill."

Pictured: "murder death kill."
Italy's armies were as shitty in the Renaissance as they were during World War II, and nobody knew this better than Niccolo Machiavelli of the Florentine militia. Throughout his classics texts The Discourses and The Prince, he cites countless examples about how a New Roman Empire was thwarted due to self-inflicted gunshot wounds to the foot. Italy's problems were twofold: one, a unified Italy still didn't exist, and two, Italy's dukes and princes outsourced too much of their military to Swiss mercenaries. Not only was this an enormous drain to so many kingdoms' economies, but many mercenaries happened to double-cross their employers for an even larger profit by skipping town. In short, Italy needed a local army built from the ground-up on reliability.

Veni, vidi, Vinci.

The science behind the [ame="http://www.youtube.com/watch?v=RITE-FiW5Gg&feature=PlayList&p=A6674B74E81FA426&playnext=1&playnext_from=PL&index=60"]"Pull it out!"[/ame] scene.
#7.
The Cluster Bomb

- Leonardo da Vinci
"Cluster bombs can kill a whole ton of shit at once."
-Anyone who's ever seen a cluster bomb in action.
Da Vinci's Design:

He named the guns "Great Vengeance" and "Furious Anger."
The Hundred Years' War saw the return of huge armies of infantry onto European battlefields for the first time since antiquity. Since the largest of these were found in Spain, France, and the Holy Roman Empire (due to their population), the divided city-states of Italy simply could not shore up the numbers for defense.
With such lopsided odds working against the Italians, more practical weapons than syphilis were needed to cripple their enemies. What was needed was a device that could annihilate entire armies before they even came close to the front lines, and da Vinci's cluster bombs had the range and splash damage to accomplish just that. As long as you provided your bombard crew with enough of da Vinci's ammo, you could dictate the fate of entire armies like the Gods of Olympus.

How da Vinci would have taken Helm's Deep.
The Evil Lair

- Leonardo da Vinci
Among Sun Tzu's many observations in The Art of War, there is "invincibility lies in the defense, and the possibility of victory in the attack." While as timeless as a tall glass of Ecto Cooler with vodka (we call it a 'Ghostbuster'), da Vinci put an interesting twist on it by removing the whole "possibility of victory" for the attacker part. When he designed a fortress, he had invincibility in mind.
Da Vinci's design:

All it needs is a weather machine, and some dragons.
Since da Vinci was born one year before Sultan Mehmed II captured Constantinople in 1453, he spent most of his life living through one big "shit just got real" moment in Renaissance warfare. Mehmed's cannons were big enough to besiege a city from over one mile away, and the loss of Constantinople--considered the last, living relic of Rome--made every kingdom in Christian Europe reach for their rosaries. The threat of the Muslims was back.
Since Turkish cannons had just made medieval castles obsolete, engineers like da Vinci were employed to soup up defenses. The fortress he envisioned in his Codex Atlanticus was strong enough to withstand any weapon from the period: artillery, siege-ladders and whatever black magic the local White Wizard might conjure.

Ditto for Saruman's Uruk-hai.
#5.
The Super-Scythed Chariot

Da Vinci's Design:

The Ferrari Armageddon.
Why it Would Have Worked:
The Italians had two priorities when it game to Renaissance warfare: winning battles, and looking good while they did it. Can you guess which of the two was given the higher priority? Hint: It involved having really large balls (and no, we're not talking about bravery).

The Renaissance equivalence of a wheelie.

The Renaissance equivalence of a clusterfuck.
