A shotgun, also called a "scattergun", is a firearm designed to shoot a multitude of lead or steel balls of varying sizes. This makes it very effective at hunting game, greatly increasing the weapon's hit potential. However, the accuracy and power found at close range diminish rapidly as you get farther away from the target. Shotguns designed for military use are often called "combat shotguns".
The Winchester widowmaker shotgun is a double-barreled 12 gauge shotgun with a mahogany grip. It also comes in a sawed-off variant. It has decent damage, but terrible range. Still, it is an all-around good weapon for early in the game. Compared to the sawed-off version, this has a 2-point-lower max damage, and requires both hands, but has doubled range.
Sometimes this gun can critical hit anybody for 93 points.