Tough question. Mine would have to be my S & W model 28 .357 with 6 in barrel. Good home defense gun and it has taken 6 deer. It would be a bit much for small game if SHTF.
a 16" AR-15 with a fixed carry handle. can hunt and deffend with it at close quarters or long distances. parts and ammo would be redily availible for many years to come during and after a SHTF scenario. Easy to maintain and very durable. reliable in many environments.