A shotgun. You can't miss, it won't go through the wall and kill your neighbor, and it looks and sounds intimidating.
You're wrong on most counts. You can miss with a shotgun, and it will go through a wall and kill your neighbor.
Have you ever checked the pattern of your shotgun at cross-room range, say 7 to 10 yards? It's not very big. You can miss.
Have you checked the penetration of your load through two sheets of drywall at 7 to 10 yards? Drywall is not armor.
Try to find "Tactical Loads" for your 12ga, both slug and buckshot. Lower velocity and less recoil, but still a huge hole. You're shooting vermin accross a room, not a buck at 50 yards.
A pump shotgun does look and sound intimidating. That's why I have one by the door.