I would say a 5 shot pump shotgun is the way to go if you need one all aroud gun. Get it with two barrels and you can hunt just about anything with it, not to mention it's one heck of a good home defense gun. There are a few good brands on the market for a good price, Remington and Mossbrg are both good guns for the money and you can get a bunch of add ons for them too.
Mossberg 500, Remington 870. Do not get the Mossberg 590, the barrels do not change all that well I am told. If you are worried about salt just maintain the weapon, we never had issues overseas in the worst locations for rusting. I would not get a pistol grip, these are for people who know what they are getting into, definitely not for hunting. I have one with such a grip and it can be a handful.
A pump shotgun in 12 ga., with 20-28 inch barrell is about the most versatile single hunting gun available. The Mossberg 500 and Remington 870 are the two current best coices in value for money.
With 12 ga slugs you can shoot deer size game out to 50 yards- with rifle sighted barrell even to 80-100 yards with acceptable accuracy. With birdshot you can take small game, such as rabbit and squirrel economically, as well as most game birds. You need special non toxic shot if you hunt waterfowl, but that is a whole nother story.
By adding a rifled slug barrel you can shot sabot slugs out to 100-150 yards, if you need that capabilty.
Later, if you want to expand your hunting capabilities, a .22 rifle for small game, and a centerfire for larger game will give you a pretty complete set-up.
For my son, who is in college right now, I bought a used Rem 870 Express for $190, a used Marlin 336 in 30-30 for $260, and a used Remington bolt action .22 Model 513 for $50, and I feel that gives him a complete range of hunting options.
Mossberg 930 SPX. It's well built, semi-auto, the magazine tube can be expanded, it's a full stock, many other plusses. This shotgun can be used for both tactical home defense, and for bird hunting with multiple different types of shot, or for deer hunting using sabot or solid slugs.
i'd go with remington 870 with some extra barrels to suit your task at hand, the 870 is very adaptable, i have a new 20inch barrel that my local gun smith sold me that allows me to use differrent choke tubes, so now i have a compact shotgun that has a very tight pattern with #4 buckshot that holds 41 pellets, one of these loads is very deadly within reasonable shooting range.
I was in your shoes about three months ago, looking for a gun to fit the same bill. After looking for about a month at every major brand and some not so major, I decided on a Remington SPR 453. It's a gas operated semiauto 12 guage chambered for up to 3 1/2 inch shells. It's basically the same gun as the Mossberg 935 but all the internal parts are steel. The Mossberg has a few plastic parts in their guns. These parts wear out and when they do wherever you might be, you are stuck with a big steel walking stick to rest on while watching all your buddies kill all the ducks.
I like the semi auto since part of your intended use is home protection. This gun requires at least 100 shells of 1 1/4 oz or greater to break it in. I put 150 shells of 3 1/2 inch 1 3/8 oz load to break mine in. Now it shoots anything I put in it. The gas system is adjustable which allows it to function with light 7/8 oz loads all the way up to the magnums. Another advantage the semiauto is much faster than a pump, especially in the hands of a person under heavy stress, like waking up to someone kicking your door in.
And the BEST thing about this gun is it costs around $450.
You might like something else though or find a deal that too good to pass up. Alot of guns will fill your needs, it's the gun that you are comfortable with and makes your job as a shooter easier.