Crossbow, Shielded (3.5e Equipment)
From D&D Wiki
This heavy crossbow has been modified with a specially designed buckler mounted on the front. A small slit in the buckler allows the weapon to be fired normally. For all purposes of combat, it is treated as a heavy crossbow, except that as long as it is held with the front facing outward, it provides a +1 shield bonus to AC, in addition to any other shield bonuses, such as from normal shields.