While most of his designs were never produced due to limitations in metallurgy and technology of that era, their ideas were highly impressive, according to Ancient-Origins.
Leonardo da Vinci is remembered as one of the greatest artists of all time. He is most famous for the painting Mona Lisa and The Last Supper, while the Vitruvian Man is now a cultural icon. However, Da Vinci is also remembered as a technical genius, including weapon designs considered 'ahead of their time'.
Although most of his designs were never manufactured due to limitations in metallurgy and technology at the time, their concepts were highly impressive, according to Ancient-Origins.
Tank
Perhaps one of Da Vinci's most famous weapon designs is the tank, especially after this type of weapon appeared in the popular Assassin's Creed series of games. Da Vinci's tank design takes the form of a circular disc, covered with angular steel plates that can be adjusted to protect it from enemy attacks. This machine is equipped with a large number of cannons mounted around it, allowing the tank to attack from all angles. Inside, 8 people control the vehicle manually with a rotating crank and gears.
This tank is truly a formidable weapon - if not for a major design flaw that rendered it inoperable in reality. As such, a prototype of the tank was constructed for testing, but researchers found that the transmission system did not work. The way the gears were set up rendered the tank completely immobile.

According to historians, such a basic mistake seems peculiar for a genius like Da Vinci. Therefore, researchers believe it was an 'intentional' act to ensure no one copied his designs, or because he secretly was a pacifist.
Long Range Weapon
Many of Da Vinci's weapon designs never progressed beyond the conceptual stage on paper, and the long-range weapon is a prime example. As a passionate historian, Da Vinci was fascinated by ancient history and ancient warfare. Many of his efforts were aimed at perfecting the long-range designs of the Romans and Persians. Accordingly, Da Vinci's long-range weapon would be horse-drawn and controlled by a knight. This weapon model is equipped with rotating blades at the front and rear, creating destructive force like a giant lawnmower.

Unmanned Vehicle
Da Vinci also conceptualized the design of the world's first unmanned vehicle. It is a three-wheeled vehicle propelled by springs to rotate the wheels. Initially, historians thought this vehicle was a peculiar creation until they realized the springs resembled leaves, allowing them to create a practical prototype.
So how can an unmanned vehicle become a weapon? Quite simple, the user just needs to load explosives and ammunition onto the vehicle before sending it rolling autonomously towards the enemy.

Aerial Screw
Perhaps Da Vinci's most famous design is the aerial screw. Often considered a precursor to modern helicopter designs, the aerial screw has rotating wings to generate lift.
According to Da Vinci's idea, if lift could be generated, both the machine and the controller could take off from the ground. Although it's not inherently a weapon itself, it's easy to understand why any military would be interested in equipping such a device for reconnaissance purposes.

Triple Barrel Cannon
Leonardo da Vinci is said to have been fascinated by the idea of a multi-barrel weapon. In the case of the triple barrel cannon, the gun barrels are designed to fire continuously in sequence.
However, Da Vinci soon realized that the weakness in his design was that the cannons could overheat quickly. To overcome this issue, the device was designed so that the barrels could be easily removed and replaced with new ones that could be reloaded and fired. Notably, Da Vinci's triple barrel cannon was actually manufactured and put into operation.
In the 20th century, the cannon was found in a fortress. In 2011, historians confirmed this to be Leonardo da Vinci's design. Accordingly, this weapon was used by the Venetian forces during the conflict with the Turks in the Renaissance period.
Giant Crossbow
Leonardo's giant crossbow was designed to be a siege weapon capable of firing giant arrows or boulders at the defensive walls of enemies.

The giant crossbow measures over 25 meters. With 6 installed wheels, it can move around the battlefield. Operating manually, the giant crossbow doesn't require many operators, as only one soldier is needed to load arrows into the firing groove and wait for the command to fire.
However, this turns out to be a design considered not truly effective. Da Vinci designed it as a cheap alternative solution to expensive cannons. However, in reality, guns and cannons outperformed the giant crossbow in every aspect.
'Harmony Organ' 33-barrelled
True to its name, this weapon consists of 33 cannons arranged in a fan shape in rows. Da Vinci's purpose in designing this type of cannon was to address two major issues with conventional cannons: slow firing rate and lack of accuracy.
The 33-barrelled Harmony Organ by Da Vinci can fire multiple cannonballs simultaneously. While one row is being loaded, the next row can be fired, allowing for continuous firing. Moreover, the cannons arranged in a fan shape enable this weapon to increase accuracy after each volley.

Its wide-ranging destructive capability makes it an ideal weapon to counter large advancing armies. It is also designed to be lightweight and equipped with wheels, allowing the cannon to move easily across the battlefield. However, there is no evidence to suggest that this type of weapon was actually manufactured. Da Vinci later designed a smaller 11-barrelled version, but it seems this version also remained on the drawing board.
Reference Ancient-origins.