Crossbow
The Crossbow is a long awaited weapon for the Assassin's Creed series. This weapon was originally seen in a trailer/intro for the first Assassin's Creed game, but was not included due to historical inaccuracies.
The crossbow has been confirmed as a weapon in Assassin's Creed: Brotherhood. After being spotted in concept arts, and being mentioned in the E3 2010 Single-Player walkthrough, Jean Francois Boivin stated that long ranged weapons such as the crossbow will be available to be used in the game, especially in advanced horse combat.
Since it is a weapon that requires ammo, arrows and/or bolts are suspected to be purchasable at the Blacksmith. It is unknown what the maximum amount of ammo for the Crossbow is or if the amount could be maximized by upgrading pouches at a Tailor if the economic system remains the same as it did in Assassin's Creed II.