Packaging components of a hunting kit as a mobile unit, you'll eventually avoid embarrassment in the field. While I don't have a kit for each type of game I hunt, I keep my go-to pack equipped with what I'll need in the backcountry. That kit includes a few items not usually carried in a pack. Deep in a wilderness area, a day's trail ride from road's end, what you lack, you'll do without.
I'm not a traveling gun shop. Nor would I relinquish my only sling to a partner on a hunt--at least not until my tag was notched--but I've learned over the years to take an extra sling. Slings can break or otherwise fail. Packing an extra, you'll save yourself searching 419,652 acres of conifers and rock. A sprung swivel can leave you slingless, too. A Latigo sling is always in my kit. That's partly because I depend more than most hunters on the sling's support when shooting. I'd as soon borrow a Depression-era scope as install a carrying strap in place of my sling.
You no doubt have most other necessary items: water, knife, compass, flashlight, fire-starting material and igniter, toilet paper, flagging ribbon, parachute cord, emergency rations, first aid kit, camera. Here are some additional thoughts.
While I think it un-American to buy or sell water, I've found plastic water bottles useful, and I once carried a plastic Forest Service canteen in a belt pouch. Both options make sense. A water bottle from a bike shop or REI works, but in my view it's unnecessarily bulky. My knife is a folding Gerber my wife gave me decades ago. Myriad other folders also give you the straight, slim, four-inch blade I prefer. More compact knives suffice if you're not after elk or moose. Field-dressing big animals, and skinning and caping them, you may find fixed-blade knives superior to folders. My favorite models are by Knives of Alaska. Its DiamondBlade steel stays sharp after other edges have dulled. I often supplement my main knife with a small pocketknife. Hunting in Africa, where long thorns have penetrated to pin my foot to my shoe, I now carry a small Leatherman. It does more than extract thorns, and it weighs little.
The best flashlights, in my view, are made by SureFire. One saved my bacon on a mountain goat hunt that brought a winter storm to the high rock during our descent. Negotiating goat terrain in the dark, in swirling snow and wind blasts that match prop wash from a P-51, you'll appreciate a strong, reliable beam in a housing stout enough to bounce off stone. Among the many SureFire models are those with an instant choice of colored lenses. Blue excels on a blood trail. Red apparently disturbs animals less than white, and white gives you the most illumination. I carry extra batteries or an extra light with fresh batteries.
You can use toilet paper for starting fires, but I prefer cotton balls saturated with Vaseline. I tote them in old film containers. They ignite easily and burn long enough to ignite kindling. Another option for the woods-wise is to pack "pitchwood." These pitch-laden pine slivers aren't found everywhere, however. Magnesium shavings and a metal match are the commercial alternative. Many hunters carry cigarette lighters to provide flame. Waterproof matches are a fall-back. I carry two lighters. By the way, fire gives you more than heat for survival. It provides companionship and comfort, something to nurture and a place to rest while weather passes or during a midday lull in game activity. Your ability to start a fire is part of being prepared for life afield.
You're smart to carry a roll of flagging tape. With it, you can show your location in an emergency or mark a blood trail to downed game. I prefer orange, though pink is as visible. Be sure to pocket the used tape when you leave the area. Incidentally, my kit has two inexpensive compasses; if I don't believe one, the other will confirm that I'm wrong.
I often carry two cameras, a pocket model in addition to my SLR. My main binocular, an 8x32 Zeiss, is always with me. But packing an extra lightweight glass makes sense. You might have to loan one or suddenly grab pack and rifle without a chance to snare a binocular.
Little of the food in my pack--usually raisins, bagels, cheese, apples and granola bars--survives a long day afield. Better to squirrel away a small packet for emergency only and change it every autumn. Include high-calorie, high-protein bars and, if you like, a couple of freeze-dried Mountain House dinners. You won't feel the extra weight--or the tug of a small first aid kit, which should include gauze bandages, medical tape, antiseptic and lightweight rubber tubing that can serve as a tourniquet. An emergency shelter is a good idea, but it adds considerable weight and bulk. Mine is a big orange trash bag of heavy polyethylene with a hole in the bottom. I can stick my head through the hole and let the bag drape around me. It seals off wind and traps body heat. It's easy to spot from the air.
I prefer a lumbar pack over a fanny pack or shoulder-style day-pack. It's big enough to hold all I want to tote, but it doesn't get in the way. A broad belt plus shoulder straps let me adjust weight distribution often for comfort on long trails and stability in steep places. The bulk of the kit rests in the small of my back when I'm crawling instead of pressing on my shoulders or bouncing. As on larger packs, I insist on oversize, heavy-duty zippers and tabs. A flat pocket in back secures an envelope with all my hunting tags and licenses. I don't use that pocket for anything else, and I don't open it unless I need a tag. Last fall, a hunting partner lost a license he'd hastily stuffed in a pocket. His backcountry hunt would have ended had the outfitter not spied the paper at a stream crossing the next day. You wouldn't stuff thousands of dollars in cash in your jeans before hiking and riding saddle stock in the wilderness, but that's just what you're doing when you slip a license into a pocket. Treat your kit as a unit; keep it complete and free of extraneous stuff. When you're easing onto a ridge before dawn on opening day, you'll want to know your kit is complete. After all, you have more to think about than what might be missing.