Blacksmith

Blacksmiths could be found all over Renaissance Italy, and sold various weapons, pieces of armor, and ammunition, as well as repairing any piece of armor they sold.

Most equipment was available in any Blacksmith in any city, however only the Blacksmith store in Monteriggioni would sell the Condottiero War Hammer and the Sword Of Altaïr before the Siege of Monteriggioni.

Repair
Blacksmiths repaired both broken and partially broken armor. Ezio could get all of his equipped armor repaired at once or individually. The cost to repair a piece of armor varied with its quality and where it was worn.

Armor
Through the progression of the game, a wider variety of armor became available for sale, and the cost for armor increased whenever Ezio bought a piece.

Weapons
Several Swords and Maces were sold, However, they did not sell Spears, Halberds, Claymores and Axes. The cost of each sword and mace increased whenever Ezio bought a weapon.

Small Weapons
The Metal Cestus and various Short Blades were also available. The cost of each increased whenever Ezio bought a small weapon.

Ammunition
The ammunition available for sale increased as Ezio progressed. Ammunition included Throwing Knives, Smoke Bombs and Bullets. During his stay in Rome, once the Crossbow was bought, Crossbow bolts became available.

Trivia

 * Blacksmiths seem to be more brash towards Ezio than the other merchants, blatantly admitting surprise that he is able to afford any of their wares. However, in Assassin's Creed Brotherhood, they are not so brash. In Assassin's Creed: Brotherhood they will say things like "One man's coin is as good as another's" when Ezio buys something from them.
 * When going to a Blacksmith in Assassin's Creed: Brotherhood, Ezio has the option to sell trading items for different amounts of money.
 * In Assassin's Creed: Brotherhood Ezio unlocks special armor and weapons such as the Captain's Sword and the Seusenhofer Armor by completing shop quests (which require different amounts and kinds of trading items) as seen in this picture.
 * The Blacksmith in Monteriggioni somehow obtained The Sword of Altaïr, even though it was Altaïr's possession.