Phantom (3.5e Equipment)
From D&D Wiki
This elegant, gold-decorated, ranged weapon seems to lack a proper string, and yet is as curved as it would be were one fixed to it.
Ranged weapons with the Phantom property use no ammunition. When the owner of a bow with this property attempts to use it in battle, a faint pink glow appears in the shape of both the invisible string and a shimmering arrow of pink light. This glowing arrow can be fired normally, and deals damage as a normal arrow of its size. The arrow disappears after it hits or misses its target. Crossbows endowed with this ability shoot glowing bolts of green light, and also have phantom green strings. They automatically create another bolt, but the wielder still needs to "reload" the crossbow for this bolt to appear. Repeating crossbows gain no advantage from this enhancement, though the bolts they fire will glow green until impact. Firearms and slings blessed with this property shoot glowing blue bullets of their size, and firearms also have blue muzzle flashes. These firearms still have to have their mechanisms cycled, but this takes less time than normal - firearms that reload as full-round actions instead reload as move actions, and firearms that reload as move actions instead reload as free actions. This weapon enhancement cannot be placed upon single-use ranged weapons, such as throwing daggers or javelins.