Just one firearm.
For home defense
For self defense
For hunting
For the range
For everything
The military knew decades ago only one cartridge was close to a one size fits all. First it was the 30-06, now the 7.62. For flexibility and firepower, that means an AR10/LR308, or a M1A which is not so great indoors for home defense.
But, I suspect most of us would ignore any law stupid enough to try and limit us to one firearm, and have something else stashed away.......1911, 870,,,,,,,,,,