10. Punt Gun
A punt gun is an extremely large shotgun used in the 19th and early 20th centuries for shooting ducks.
It could only be fired from a punt, a type of small boat. Punt guns were usually custom-designed and so varied widely but could have bore diameters exceeding 2 inches (51 mm) and fire over a pound (≈ 0.45 kg) of shot at a time.
A single shot could kill as many as 50 ducks at once.
Eventually, the punt guns killed so many ducks that their population declined precipitously and by the 1860s most states had banned the practice.