Let's say you have unlimited money and acess to all the best tooling and engineers in the world. What do you build first? Here's mine:
Type: Revolver
Caliber: .22 rimfire (interchangeable cylinders for .22 LR and .22 WMR)
Capacity: 12
Action: DA/SA
Cylinder: Swing-out
LMG with AK-style wood furnishings that shoots an armada of miniature robot
that automatically dig into entrenched positions in the entire area to kill any approaching fascists. Has an engraving that says "this machine plays folk music".