1.) .375 H&H
So many talk about one cartridge that can do it all, and H&H's classic comes the closest. Day in and day out, it ends stare-downs with elephant and buffalo, and then puts 30-pound antelope in the pot. Long range or up close, the .375 H&H's inherent accuracy, manageable recoil and knockdown power put the "able" in renewable resources.
2.) .22 LR
If you like to shoot a lot, here's a lifelong buddy. I hate to think about the world without the .22 LR. Nowadays, it's underappreciated for hunting, and worse yet, many kids have never shot a .22.
If I had to own just one gun ... I'd rather plug deer and elk with 12-gauge slugs than try intercepting pheasants and mallards with a .30-06.
The all-time all-American caliber really can stop every game animal on this continent and has done so countless times. With the exception of pursuing King Ursus into the willows, any shortcoming of the .30-06 is on the shooter.
5.) .270 Win.
Thanks in part to great PR, the .270 Win. opened America's eyes to the prospects of shooting big game way out yonder. Let's pretend that stultifying "Is it good enough for elk?" argument never happened. With straight shooting, the .270 is good enough for anything short of dangerous game.
6.) .243 Win.
This is the gun culture's equivalent of the little engine that could. You certainly could fill your deer and pronghorn tags with the overachieving .243, and a pile of caribou tags to boot. You could also count on long-range predator performance.
7.) .500 N.E.
Though the Nitro Expresses aren't homegrown rounds, perhaps they should be. Given our big American obsession with raw power, how can we not be in awe of a sporting rifle that tosses a 570-grain, half-inch-diameter hardball at 2000 fps? When they get the bugs worked out of that Jurassic Park thing, this is what I'm taking.
8.) .30-30 Win.
Give gramps his due. The old .30-30 ushered in a new American century, helped to put blackpowder out of business (temporarily), and never met a 150-yard deer or black bear it couldn't whip.
9.) .284 Win.
With its rebated rim and feeding issues, the .284 didn't last long in the production-rifle arena. But its legacy lives on. The cartridge spawned a class of short-action, bantamweight rifles chambered for stubby-but-potent calibers.
10.) .300 RUM
Remington's supersized .30-caliber Ultra Magnum was all but dismissed as pointlessly powerful and too recoil-abusive, and then was left for dead when short-mag mania hit. But someone forgot to tell serious Western hunters, who go to great lengths for great trophies.