Here is a 20-gauge Baikal Coach Gun with a Winchester 1894 Ranger Compact in .357 Magnum. Both are nice bedroom pieces.
The Coach Gun is loaded with #3 Buckshot which has 20 pellets in the shell. The Ranger Compact is loaded with 158gr JHP. Either one will work well for the intended purpose. #3 Buckshot is .25 caliber so you are putting a good amount of lead in the air when you fire it.
You do have to aim with a shotgun instead of the common myth that you just point it in the general direction. There is nothing more intimidating than hearing the sound of a pump shotgun racking or looking down the twin muzzles of a double barrel shotgun.
One time I came home in the early morning hours from an out of town job when I lived on the family farm. It was about 3am and someone had locked the door for some reason. I came in through the Bilco basement door to get into the kitchen. It woke up my Dad's Doberman Pinscher and Dad.... I opened the door to the kitchen from the basement to find myself looking down a double barrel 12 gauge!!! I swear it looked like 2 open 55 gallon drums!! I had to swallow my heart and check my pants for a brown stain after seeing that.... I explained that someone had locked the door and I was trying to get in without disturbing anyone. We did get a laugh from it but I can close my eyes and still see those huge holes looking at me ....