This is a bag that I've had for nearly thirty years now. I got it at a Foley's, it was a bonus with some holiday cologne purchase, and it's basically a canvas with leather trim larger sized doctor's or train bag. Probably about 16" long and 14" wide, with a very cool large hidden pocket on one side and a large outside pocket on the other. It has a hard bottom of some sort.
The large hidden pocket with a heavy duty zippered opening is large and sturdy enough for my Thompson Contender pistol and a small cartridge belt of shells for it. So it will pretty much hold any other pistol I own with ease. Normally, a larger caliber handgun goes in this pocket, such as a Glock .45 ACP or a 4" .357 Revolver, along with a holster, extra ammo/carrier. Each gun will be loaded with shotshells for the first couple of rounds then ball or semi-wadcutter (.357) rounds.
Inside the front outside pocket is a good place for the snake bite kit, extra knife, small first aid kit, flares and one of the .22 pistols and a small box of .22 ammo. GPS. Compass. Flashlight and extra batteries. Some carbiners.
Inside the main part of the bag goes the fishing gear. A spare baseball cap. A pair of gloves. Some bottles of water and bags of juice. Peanuts. Energy bars. An empty belt bag, for carrying stuff in when you're afield. A good hank of rope, about 50' to 100' long.
Other contents vary as to what part of the State I'm going to, but there's a small shoulder creel/bag made canvas that I carry inside that has the basics that go from place to place on nearly every fishing trip. The creel has two sets of needle nose pliers, a leatherman tool, a plastic dehooking device, wire cutters (in case someone gets hooked and you need to cut the barb off of the hook to get. it. out. Ow. Very recommended. I carry several different types and sizes of small wire cutters, in tackle boxes, bags, etc. Needle nose pliers with a cutter can do in a punch, but there are some better tools available for cutting fish hook barbs off.) a filet knife, a small folding knife.
Normally I'm carrying fly fishing gear whenever I go fishing, just in case. I've got an Orvis Frequent Flyer rod that fits into this case, as well as a nice 80's Fenwick ultralight spinning rod. A reel for each of those rods, a very small shoulder bag that carries fly boxes and my necklace "fly vest".
Then, there will be several small plastic tackle boxes, containing lures appropriate to the fish and locale I'm heading to. Sometimes I'll throw a live bait box in along with this bag, that has all kinds of live bait stuff, particularly for catfishing. I also have a small Plano double sided box with a shoulder strap set up for river fishing in Texas. It's got a selection of spinners and plugs and lures and live bait fishing stuff in it and will even hold some pliers.
I've got larger tackle boxes for larger lakes and waters and different kinds of fish and a ton of vintage/garage sale/ gimme lures gathered from over the years grouped by type of lure and these tackle boxes go into bags that hold them. Lots of these old lures are classics but were beat or had bad hooks or paint or hardware or were discolored or whatever and I've repaired/refurbished them and they have no collector's value so they are fishing fodder. For example, I got for several dollars a collection of plastic "Mudbug" lures that scrape the bottom of lakes stirring up muck and mud and supposedly attracting all kinds of LARGE bass. They were all the rage in the 70's, but I got mine from a garage sale in the lae 80's. I have a collection of like 20 of those that need to be fished at the right lake on some kind of gravel grade, clear of weeds and such.
So despite all of the gear that might come along with me, the kit bag remains near constant. It has a couple of plastic boxes of lures for the ultralight rod that will work in areas I'm likely to be, and I can throw any number of other boxes in the car to take with or exchange for what's in there. Generally, across Central and East Texas, it's gonna be the same stuff, with just a few different and smaller/larger lures in the Hill Country.
So the bag sits by the door, waiting only for the guns and juice and snacks, ready to go. If I jump in the car and head into East Texas, it's ready. If I head west, it's ready.
And if I'm heading south to the salt, the freshwater rods, reels and lures come out of the kit bag but the creel bag and tools stay in and the kit bag goes to the beach. I put my nicer saltwater reels in the kit bag, along with fly fishing stuff for salt water fly fishing and again, the necklace fishing vest. Usually, there's a Curado, several AbuMatic 290's and a surf fishing reel. The more workhorse reels stay on the rods in the SUV.
I've tried to find another kit bag to use for saltwater, but it's no use. I even found a very cool backpack with a rubber waterproof bottom and liner that I used for some years. But to no avail. This kit bag has been on so many adventures with me over the years that it's an old friend.