Light Crossbow of Acid Arrow (3.5e Equipment)
From D&D Wiki
Light Crossbow of Acid Arrow: This fairly common magical crossbow is a +1 light crossbow of acid arrow. It appears as a normal crossbow, but it is in reality an effective magical weapon. When the wielder pulls back the lever or ratchet to load a bolt, a magical bolt appears on the bow. When the bowman fires the bow, an acid arrow is flung from the tip of the crossbow (as per the spell). This saves the user from having to reload the crossbow. The crossbow must be aimed and fired as normal - the magic within this crossbow does not send the acid arrow unerringly to it's target. The wielder must make a normal ranged attack, rather than a ranged touch attack to hit with the weapon. This weapon is for all purposes a regular crossbow and exhibits all properties of a regular crossbow, including the ability to perform a ranged sneak attack.
The Light Crossbow of Acid Arrow can also fire normal crossbow bolts.