bgaesop wrote:Get a good .22 rifle for a longarm, or a .410 shotgun is what I've heard.
Or an over-under combination gun for the best of both worlds.

However, I'd recommend a 20-gauge over a .410-bore. There are also drillings (3-barrel) and vierlings (4-barrel), but these are high-end custom pieces that are
always unreasonably expensive. The most common drilling configuration is two shotgun barrels (same gauge) over a rifle barrel. They can be configured in different ways, though, and there is such a thing as an all-shotgun drilling with a triangular barrel cluster (usually two-over-one from what I've seen). The best vierling configuration is over/under rifle combined with side-by-side shotgun. Usually, the shotgun barrels are the same gauge while the rifle barrels are two different calibers (one small, one large). But this is all trivial information since the price of these things negates their utility.
For a rifle, I'd recommend a lever-action. They're lots of fun. Unlike bolt-actions, they're ambidextrous. As for caliber, if you want something more substantial than a .22, .30-30 has ballistics comparible to 7.62x39mm. For a shotgun, I'd recommend a 12- or 20-gauge Remington 870, Mossberg 590, or Mossberg 500. If it's for defense, get one with an 18.5" or 20" barrel. With an 18.5" barrel, your highest capacity with an 870 will be 7 rounds (6+1, standard 2.75" or 5+1 3" Magnums). Defense Mossberg 500s come in two basic flavors: 6-shot w/18.5" barrel or 8-shot w/20" barrel. The shorter one handles the best and is less clumsy to lug around (especially in confined spaces). There are other specs on the 500, but these are the two most basic configurations that you should concern yourself with if you're lo0king for a combat shotgun for defense.
Then there's the Mossberg 590 -- my favorite of all standard-type fixed tube repeating shotguns. The two basic flavors are 6-shot w/18.5" barrel and 9-shot w/20" barrel. The 9-shot 590 is probably the ultimate tube-fed repeating shotgun you can buy because it already has a maxed-out magazine tube and a barrel that isn't too long. On a defense shotgun, the barrel should be no longer than 20". As a proud 590 owner, I can vouch for its awesometasticness.
16-gauge splits the difference between a 12 and a 20 but is kind of hard to find. The first shotgun I ever shot was a single-shot 16-gauge. The first shotgun I ever owned was a 12-gauge side-by-side. To break it down, I recommend a 20- or 12-gauge pump-action shotgun. As for rifles, I advise
against semi-auto .22s -- this applies even more to pistols than rifles (but doesn't apply revolvers). They're just not reliable.