You mentioned the 12 gauge for home defense - always a good choice. Winchester or Moss. are always good and not too expensive.
You might want to consider a Marlin lever action carbine rifle. They are pretty short(18 to 20 in barel) and come in .38 and .357 models. These hold 8 to 10 rounds. You can conceal these even in a vehicle pretty easily.
And the Winchester Trapper (18 inch barrel) comes in .44 Mag. :)