I had to think long and hard about this. If I were only allowed one I would sort of cheat. I would take an ar-15 with a drop in. 22lr drop in conversion.
CMMG now makes a drop in conversion for AR piston guns. The AR can also take an oil filter for sound suppression after rule of law has collapsed. When using the .22lr round with oil filter it is more quiet than my .22 Air Rifle. There is youtube video of Hickok45 using an STP oil filter ... but not with 22lr, IIRC.