Hidden Gun

"It seems to be a kind of arma da fuoco - but as small as a hummingbird!"

- Leonardo da Vinci, regarding the pistol's design.

The Pistol, also referred to as the Hidden Gun, was one of the many additional innovations of the Hidden Blade invented by Altaïr Ibn-La'Ahad using the Apple of Eden.

After discovering the design schematics for the pistol on one of the Codex pages, Leonardo da Vinci managed to craft one for Ezio Auditore, another assassin.

Description
The pistol consisted of a small firearm with a very short barrel that, if aimed properly, could kill a target from a distance. Though an excellent weapon for assassination from afar, it would give away its user's position immediately after firing, due to its loud discharge.

Up to 6 bullets could be held at a time, and could be purchased from any blacksmith. However, they were quite expensive, as one bullet cost 175 florins (149 florins with a full discount in Monteriggioni), which was three and a half times the cost of a throwing knife. Alternatively, bullets could also be obtained by looting dead guards.

Combat
The pistol took about a second and a half to completely aim, though it could be fired before it was fully aimed. Firing immediately without aiming was not advisable, as even at close range, it was highly unlikely to result in a hit.

Aiming the pistol within guards' lines of sight would automatically make them suspicious. When in combat against a small number of guards, aiming it for several seconds would also cause the group to lose morale and eventually flee, though this tactic was ineffective against Brutes.

Though not recommended, it was also possible to quickly switch to the pistol during a battle, and take a random shot from as close as possible to an enemy, before resuming the fight. Despite its low success rate, this method could potentially pick off immobile opponents, or quickly eliminate enemies without the need for counter-kills.

Advancements
Some time before the Siege of Monteriggioni, the aiming method of the pistol had been modified, and no longer required a trigger pull to be fired (an invisible mechanism similar to the hidden blade's). Though perfect aim was achieved much more quickly, the bullet could only be fired after the shot was fully charged.

Ezio also gained the ability to dual-wield the pistol alongside a medium, primary weapon; such as a sword or warhammer. It allowed him to seamlessly switch between short and long ranged combat in battle, using the pistol with his left and a sword with his right.

Ezio also used the pistol for counters and point-blank kills during close combat; for example, Ezio could sword-counter an attacking enemy, then instantly fire the pistol on another, killing two guards at once.

After reuniting with Leonardo da Vinci in Rome, Ezio was able to purchase an upgrade to his pistol that allowed him to fire small poison darts from it, in addition to bullets. These darts were usable when the poison blade was equipped, and shared its effects, allowing him to quietly and cleanly kill targets at a safe distance.

Though not used by Ezio, Leonardo also created an alternative to the pistol called the hidden bolt, which could fire small crossbow bolts instead of bullets. This modification was requested by an apprentice of Ezio's, Francesco Vecellio, as Ezio had not allowed him to carry a pistol.

Codex Description
"Success! We have found a way to alter the structure of the hidden blade so that it can be used to launch small projectiles. It is capable of grievous damage – even from great distance. I confess, the means by which I came about the discovery was... risky to say the least. But I have found that in small doses, and with a focused mind, the Apple can be used without ill effect. Or so I hope.

"The knowledge of projectile combat is not new to us, having been observed amongst our Eastern neighbors. But their weapons were much larger – and insufficient for our needs. I have now found a way to miniaturize their designs, embedding their fiery weapon into a form that can be worn on the wrist.

"We have also refined the formula for combustible powder, such that common ingredients might be used. This is a dangerous bit of knowledge and it is best shared with only our closest allies..." -Altaïr in Codex Page 28.

Assassin's Creed II

 * Often when the pistol is fired, a dog can be heard barking. However, no dogs are seen or mentioned in the game.
 * Both the pistol and throwing knives are disabled in the Secret Locations that require the player to chase after an Agile guard.
 * The pistol does not kill in a single shot during the battles with either Dante Moro or Rodrigo Borgia, though it is just as effective as usual when the player is required to assassinate them.
 * During Carnevale, Teodora suggests using the pistol to assassinate Marco Barbarigo, since the sound matched that of the fireworks being used.

Assassin's Creed: Brotherhood

 * The pistol is also a multiplayer ability for multiplayer characters; though it is unknown if they actually possessed the weapon, or if Abstergo simply added the ability in the Animus.
 * Ammunition can be found \when looting the bodies of any deceased guards, regardless whether or not they are arquebusiers.
 * Four additional bullet slots (for a total of ten) can be purchased for 30 Units on Uplay.
 * For reasons unknown, counter-attacks and executions do not use up bullet ammunition.
 * A possible design explanation is that since the pistol is automatically used during counter attacks, the player has no control over it, and it would be harsh for it to use ammunition.
 * Another possible explanation is that, when firing at close quarters, Ezio is using blanks (ammunition containing gunpowder, but no projectile), which can still be just as deadly at point-blank range.
 * During a kill-streak, the player can hold down the attack button while targeting an opponent, causing Ezio to perform an automatic double kill with his sword and pistol, using up ammunition in the process.
 * The sound of the pistol more closely resembles that of a musket, rather than the cannon-like sound in Assassin's Creed II.
 * The Assassin apprentices' pistols (obtained by rank 5) use the same firing sound as heard in Assassin's Creed II.
 * Strangely, the apprentices' pistols are much weaker than Ezio's, taking up to three shots to kill a guard; though this may be attributed to Ezio being more skilled at aiming firearms.

Others

 * The first recorded usage of the pistol was by Altaïr, when he killed rival Abbas Sofian during his arrival in Masyaf.
 * Due to connectivity features with Assassin's Creed II, it is possible to obtain a variant of the pistol that fires throwing knives instead of bullets in Assassin's Creed: Bloodlines.