More or less the only true "caliber" shotgun...don't count one out. I watched a ten year old girl back in '73 drop a doe, dead in her tracks with a .410 from about 75 feet.
True.
Now a little legal disclaimer - I do not advocate, advise, suggest or guarantee the following information. It is never safe to load and or fire ammunition from a firearm that was not designed for the ammunition or load ammunition into a firearm it was not designed for. Children, and kitty cats, do not do this at home or away!
You can load and fire a .45 Long Colt in a .410 shotgun (many experts that know nothing more than which end of a beer can to drink from swear that this is how the Taurus Judge came about). I don't know about all states, but I do know that Minnesota Conservation Officers, and several surrounding States, will not cut you any slack if they catch you hunting during slug season with a .410. Their experience is that you are more than likely shooting a rifle or handgun cartridge than shotgun slug.