My S&W 63-4 .22lr with a five inch barrel and my Kimber 84M in .308. That would satisfy my needs in the most dire of circumstances. If faced with that decision I would assume a post apocalypse situation. Both are meat makers when pressed into that role. Ammo is readily available, being found at almost every country store and quick stop.
Fortunately we live in a country and time that doesn't require such drastic measures.