I believe those who play AC Brotherhood are familiar with this. When you visit the Blacksmith early in the game, in the weapons section, there's this Captain's Sword that can only be acquired by finishing a Shop Quest named "Faith". IT instructed you to find several Items, some of them are quite difficult to obtain. What i will tell you is how to uwn a captain's Sword without having to waste your time running around looking for treasure boxes. here's how it is.

First, you need a heavy weapon. the earliest you can buy from Blacksmith is Bearded Axe. But before you can even carry a heavy weapons, you need to buy a heavy weapons pouch from the Tailor. Get both a s soon as you can afford it.

After you acquired and equipped the Bearded Axe, run aound the town a look closely at every Borgia Guards you meet. Some of them carry Captain's Sword.

When you found a guard which carry a Captain's sword, pick a fight with them. after you've finish them off, draw your Bearded Axe (if you havent done so already), hold ATTACK button, and then release. Ezio will throw his heavy weapons and your weapons slot will be empty. Go to the dead Guard's "Captain's Sword" lying on the ground and pick it up. this will automatically become you weapons and Ezio will sheath it instead of dropping it when you press O button. This can also be use on all type of swords and axes that you take fancy but aren't available to you yet, Such as Scimitar and Schiavona that only appear late in the game, Or Spada Lunga, anothe weapons that only available through shop quest.