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Here is a good option, a concealable shotgun.
Ah the judge...a 410 might not look like much, but I promise you that the .410 00 buckshot packs quite a punch...and of course you can also shoot .45 acp out of it. Another upside is you can convert it to a rifle with a simple kit.
I keep a cheapass weatherby PA-08 behind my door and some buckshot in my desk. I think if someone busted in and they heard that pump action I would turn the corner and just see their ass going right back out.