If you happen to think killing two birds with one stone is a bit inefficient, or you have to deal with a zombie apocalypse, you might be interested in a special type of gun known as a 'punt gun,' that used to be somewhat common among commercial waterfowl hunters.
What's so special about this gun? It is capable of killing upwards of 50-100 birds in a single shot. They were too heavy and the recoil too strong for a hunter to fire them by hand. Instead, they were (usually) mounted to small, often flat bottomed, boats known as 'punts.'
(via Nag on the Lake)