Hunting, recreation, self defense, home defense. Those are the main arguments I know. This generally corresponds to rifles/shotguns, plinking/antique guns, handguns, and shotguns/handguns respectively.
It's also sort of in the roots of the country, so you could say it's sort of patriotic to own a gun and train yourself in its use, but that is of course not a cold, practical argument.
Note: "Self defense" may have raised eyebrows; in particular, I am referring to people like judges and police officers who handle violent criminals. Typically these people are allowed to carry just about anywhere even off-duty.
Note2: In case you aren't actually aware, shotguns are commonly used for hunting, typically for small game and birds.
I would like to see some numbers for the home defense case -- it seems that the reasoning is mostly based on common sensical intuitions. IIRC guns in the home are multiple times more likely to be used against the family, than against an intruder. Permitted law-enforcement use is also acceptable to me.
Everything else you mentioned can, I think, be narrowly compromised on -- for shotguns, we can have single or double-barreled breechloaders only, 20 gauge only. That is plenty lethal, and the freedom to own pump-loading and larger gauges are, I think, acceptable casualties.
I think there really is not a fact-based case for the civilian ownership of the majority of weapons designed and sold in the market. Why does anyone need a Bushmaster or knockoff AK?
I'm not a big proponent of guns as home defense, I was just listing the arguments as you asked for them.
As for shotguns, while I'm partial to breech loaders, I imagine pump-loaders would be nice when bird hunting- you have literally seconds to take your shots. 12 gauge is popular for hunting, particularly when using a shotgun as a poor man's deer rifle (buckshot or slugs). Anyway, don't worry about shotguns so much. They aren't used much in crime, and I gather they are pretty survivable at all but very close range.
If you want to save lives, forget shotguns, forget rifles, forget even assault rifles- while mass shootings are big news, from a pure numbers point of view handguns are the biggest nail to pound down. More people in rural California in 2010 were killed with handguns than the count for the Connecticut shooting:
It's also sort of in the roots of the country, so you could say it's sort of patriotic to own a gun and train yourself in its use, but that is of course not a cold, practical argument.
Note: "Self defense" may have raised eyebrows; in particular, I am referring to people like judges and police officers who handle violent criminals. Typically these people are allowed to carry just about anywhere even off-duty.
Note2: In case you aren't actually aware, shotguns are commonly used for hunting, typically for small game and birds.
Note3: Skeet shooting is an Olympic sport. :)