Arrow +3

Arrow +3 is the most powerful enchanted arrow. It has a +3 thaco bonus and deals 1d6 points of physical damage. These arrows appear in Baldur's Gate II: Throne of Bhaal. They are sold by the bartender in the Tankard Tree, and the merchant in Forest North.

In-game description
"These enchanted missiles far surpass the craftsmanship of any arrow, magical or otherwise, you have ever seen."