Double Barrel Shotgun
The Double Barrel Shotgun is a lower tier, close ranged weapon capable of one-hitting enemies within its effective range. It's best used in conjunction with other, longer range guns and against only one or two enemies at a time since it can only shoot two shells before requiring a lengthy reload. Furthermore, shots should only be made with it if it's likely that the majority of the pellets in a blast will connect with their target.
It makes for a strong early game weapon because of its relatively low cost. If the extra resources are available, it's a much safer and more reliable investment than the Waterpipe Shotgun since it's not as dependent on a single shot killing an enemy. Generally, unless going into an engagement that has large group of possible enemies (like a base raid or supply drop), it'll most likely be more cost effective to take a Double Barrel over a Pump Shotgun.