I am with Josh, Rem. 870 3" mag. You can get different sized barrels, and stocks. If you going to use if for home defense, or defense in the woods, while hiking, camping etc. You can get a stock with a pistol grip. Do not get just the pistol grip. it is pretty much useless, in my opinion. Get the one with the stock, and pistol grip combo. you can put the stock under your arm, and hold the pistol grip, and finger off the trigger, at the ready, and a flash light in the other hand, held out away from your body, so if the light becomes a target, you are not behind it, while investigating things that go bump in the night. Also you can change barrels, for defense, to hunting. you can get chokes for it. The barrel will usually come with a choke already built into the barrel, full, mod, cylinder bore, Improved cylinder, etc. you can get barrels,with screw in chokes. I would recommend a Modified choke, as it is the most adaptable in most situations. If you are going to be duck, or goose hunting, get a full choke, but the Modified is the all around choke. And yes you can shoot slugs out of a full choke. The 870 is a VERY dependable gun. My second choice and right next to the 870, is the Mossberg Pump, in 3inch mag. It has the tang safety, and two slide action bars. You don't have to shoot 3 inch mags in these guns, you can shoot 23/4 inch, in them also. But the mag is a bit more powerful, and more shot capacity. A single shot is fine for back packing, or a truck, or boat gun, but when the chips are down, do you really want a single shot? Get the 870, and then look for accessories, but like I said, the pistol grip, is just Hollywood. Shoot one a couple of times, especially 3" magnum buckshot, and you will soon be putting the real stock back on. Plus you have much more control with a stock with, or without the pistol grip. Anyway, that is my two cents. I have an 870, 3 " mag, with 20 inch modified barrel, and a stock with a pistol grip, and flash light attachment. It is by the bed within arms reach, in case a bear,or other critter, thinks it wants something in my house. I have had bears in my yard, and a young one on my deck, and it showed no fear, when I rapped my knuckles against the sliding glass doors,
So I grabbed my pistol, and stepped out on the deck, and jumped, and stomped on the deck, and yelled at the bear, and it took off. But the big boy, in my yard, was a big black bear, but there are Griz, here too. My neighbor had a sow, and cub walk in front of him, as he was walking out of his shop. The shotgun, by the bed, I keep loaded with 3"inch Mag buckshot. If you are just using it for home defense, against intruders, I would suggest, number six shot, for the first two rounds, and then buckshot for the rest. You can get extended magazines for it. Number 6 shot, at close range, will cut most anything in half, and will not go through two or three walls, and hit innocent persons, as the energy will be be spent, to the point it will be pretty much harmless. Besides, even empty, just the sound of a pump action shotgun, in the dark, is universal, and gets people who should not be there to thinking about exiting as soon as possible. Good luck with your decision.
Wayne