Crossbow
The Crossbow is a long awaited weapon for the Assassin's Creed series. This weapon was originally seen in the trailer for Assassin's Creed, but was not included in the game due to historical inaccuracies.
The crossbow has been confirmed as a weapon Assassin's Creed: Brotherhood as one is seen on Ezio Auditore da Firenze's back in one of the first concept arts. Also in the Brotherhood E3 2010 Single-player walkthrough, it was said that long ranged weapons such as the crossbow will be usable during horse combat.
Since it is a weapon that requires ammo, arrows and bolts are suspected to be purchasable at the Blacksmith. It is unknown what is the maximum of ammo for the Crossbow or if the amount could be maximized, possibly by upgrading pouches at the Tailor, like in Assassin's creed II.