For a home defense gun get a Red Dot or Holo. ( an Aimpoint or EOTech, not a "blue light special."
They would we superb for TEOTWAWKI as well.
And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.