In terms of a Shotgun, 12 gauge is a given and Mossberg is the brand. Select pump for simplicity and add the extended tube with slugs or buck shot. At close range, *shudder*
Long range goes to the AR-10 .308. The AR platform is big, powerful and provides excellent accuracy at long ranges. Infection is not an issue at long range.
The everyday Tactical Rifle goes to the AR-15. .223 ammo is plentiful and still affordable. Consider the 9mm parabellum version to solve the ‘commonality of round’ issue. Parabellum means ‘for War’. ‘nuff said.
A Revolver man chooses a Colt Python in .357 for sheer stopping power. Semi-autos Pistols prefer the 1911 platform in 45acp.