You'd be hard pressed to find a more versatile cartridge than the ubiquitous .30-30 and a short, handy lever-action rifle to take it. I'm partial the the Winchester 94 as long as I can have an older one with low mileage...but the Marlins have a lot to offer, and are probably a bit more robust than the Winchesters in any event. I understand that the Marlin Micro Groove rifling isn't a good match with the new LeveRevolution ammo that's on the market...but that may be due to certain lots of undersized bullets.
Ammunition is comparatively cheap and available in the most far-flung places you can imagine. Accurate and powerful enough for deer up to 125-150 yards, and sizeable Black Bear at 75-100...and out to 250 for a human antagonist who is out to ruin your day.
If you're not limited to one rifle, a good bolt-rifle in .308 is an excellent choice, with its almost ballistic twin, the 7mm-08 a close second. The advantage is that you can easily reform plentiful .308 brass for the 7-08 ammunition, and it doesn't normally even require neck reaming unless you opt for 7.62 Nato brass. The .308 still gets the nod for ammo availability, though.
For pistol...9mm ammo is also plentiful and cheap. Good choice. For an all-around, go anywhere/do anything handgun round...take a close look at the good, old .357 Magnum in a 4-inch revolver. I prefer fixed sights for ruggedness, but adjustables may be more to your liking.
.22 rimfire is always a good bet, especially in a good quality pistol or rifle. It's just hard to beat for plinking, practice, or shooting meat for the pot. Same goes for the 12 gauge shotgun, though a light, fast 20 gauge double is a pleasure to own and use. The 12s get all the glory, but the 20 gauge shooters just smile and keep their little secrets to themselves. Handle a 26-inch 20 gauge double in close cover on quail or grouse and you'll see what they're smiling about.
