Sword of Altaïr

Altaïr Ibn-La'Ahad had a personal sword that he used throughout Assassin's Creed, Assassin's Creed: Altaïr's Chronicles, and Assassin's Creed: Bloodlines. The sword also appears in Assassin's Creed II, and Assassin's Creed Brotherhood, but is used by Ezio Auditore da Firenze, a descendant of Altaïr. The blade's hilt is shaped like an eagle's wings, while the blade itself is both long and agile, making it a light and deadly weapon. The sword is apparently the weapon of choice for the guards at Masyaf, and an all metal variation is available as a weapon in Assassin's Creed II.

Assassin's Creed
Altaïr starts the game with the Syrian sword, which he is very skilled at using, until Al Mualim demotes him to Novice for breaking all three tenets of The Creed. This decreases his abilities greatly. During his progression back into the ranks, he starts off with a basic sword similar to this, though it does not have a cross guard. After he assassinates four targets, he gets his personal sword returned to him. He uses this sword until the Syrian sword is returned to him.

Assassin's Creed: Bloodlines
Altaïr still possesses his sword during the events after Assassin's Creed, in Assassin's Creed: Bloodlines. In fact, his swords can be found hanging within Kantara Castle's Great Hall (in "The Bull" stage), as ornaments. During the game, this is the only sword that can be used. In the beginning, its attack power is quite low and enemies have to be hit with it multiple times to be killed. However, upgrades for the sword and other weapons of Altaïr can be purchased by collecting Templar coins.

Assassin's Creed II
Altaïr's sword is available in the Monteriggioni blacksmith for 50,000ƒ (or less if the store has been renovated) after DNA Sequence 8. This sword is one of the most powerful melee weapons, as all three stats are maxed out. It is interesting to note that the picture of the weapon's hilt in the blacksmith has a leather-wrapped hilt, however the weapon itself does not have any leather wrapping. Ezio wielded the sword when he fought Rodrigo Borgia in the Vault.

Assassin's Creed: Brotherhood
Because Assassin's Creed: Brotherhood takes place directly after Assassin's Creed II, Ezio Auditore wields the sword as he makes his escape from the Vatican Vault into Rome. He later loses it, along with the majority of his equipment during the Siege of Monteriggioni. The sword appears on a weapon rack in Ezio's Tiber Island Hideout once he completes all 5 Assassins guild challenges. The sword can only be equipped from the hideout. It can also be used by Assassin apprentices once they have reached rank 10, Assassino, although for them it is called the Assassin Sword. Guards can be seen wielding the sword in certain cutscenes. Ezio wielded this sword when he confronted Cesare Borgia in Viana.

Trivia

 * It is unknown why the sword is available from the Monteriggioni blacksmith, since the sword (being Altaïr's personal weapon) would be assumed to be available together with his armor once it was unlocked. However, a possible cause is that the sword had been lost along with the Codex, and was later found and sold to the blacksmith.
 * The sword in the game is shorter compared to the other longswords Ezio can use; the entire sword being only a little longer than the length of his arm. Despite this, Altaïr's sword is the strongest weapon available.
 * Strangely, though Altaïr's sword is considered the best sword in Assassin's Creed II, in Assassin's Creed, the Syrian sword (which in Assassin's Creed II was among the cheapest weapons) was the best sword.
 * It is interesting to note that, in later memory sequences of Assassin's Creed II, if the player has the sword equipped, it can quite possibly be knocked away from Ezio by Brute guards. It can, however, be re-equipped in the Villa if it is lost.
 * There is a glitch in the Xbox 360 version that automatically replaces this sword with the "Common Sword" in Ezio's inventory after it is bought. To fix this, you will have to go to the weapon room in the Villa Auditore and manually equip Altaïr's sword again.
 * During a mission in Assassin's Creed: Brotherhood, when Ezio kills and impersonates a guard named Luigi in order to assassinate Juan Borgia, a fellow guard draws and raises the sword of Altaïr. This is rather unusual, and unclear if intentional or rendered accidentally by the developers.