Double-Barrel Break-Action Shotgun
Add a double-barrel break-action shotgun that is loaded with 2 shells that can be shot rapidly, but has to be reloaded with the break-action mechanic. It is maybe not the most efficient weapon, but a fun one for sure.
Attachments: Red-dot sight, holo sight, laser pointer, barrel extension for more range.

Optional: A sawed off mini version as secondary with less range and more spread.

Peak, but optional would be to empty the fired shots, that you hold up the gun to let the shells fall out and when loaded, to swing it up to close the barrel again.