Shotgun: Mossberg 500 'cruiser' (extra capacity tube 7+1)
Rifle: out of what I currently own, it'd be my Marlin 336-BL 30-30. Out of what I want to own, it'd be a S&W AR-style 5.56
Pistol: Probably my SW1911, very accurate, adequately powerful, and I also have the kimber .22lr kit and four .22 mags for it (if that's allowed in this hypothetical survey) but honestly I'm on the fence. Its a toss up between SW1911 or my SW5906, because when it comes to the center-fire ammo, I can carry a decent bit more 9mm than .45 in less mags too, for a small sacrifice of impact-force. (i like the .45 better, but if it's a go-to-war gun, and we can only have one pistol, I have to think about maximum ammo I can carry)