Automatic Crossbow (3.5e Equipment)
From D&D Wiki
An crossbow automatically pulled by a wheel with a slider. One of the deadliest weapons, invented by a thirteen year old, who now travels around selling them at extremely high prices.
Fires 3 times with a standard action, or 5 times with a full round action. Clip is 15 bolts, costs 10gp per clip Can be used with one in each hand, at standard penalties. You can reload with one in each hand.