The Belial, a 10-gauge lever-action shotgun usually associated with mercenaries and vigilantes. It's long lifetime means it's gone through multiple manufacturers and independent gun foundries, to the point where the original model is considered a rare find among collectors.
The Belial is well-known for it's amazing rate of fire, as compared to it's competitors. In the hands of a expert, it is capable of releasing 20 rounds per minute.
In addition, a good deal of the gun's parts are modular. This has led to such insane custom versions as a "Scatter flamethrower" which releases multiple incendiary rounds in a short time.