h/t Total Survivalist
Ryan gets it about as near to perfect as it's possible to get.
And, as both he and Commander Zero have noted, a wad of cash and a credit card with a high limit solve most regional disaster problems too.
(Hurricane? Brushfires? Earthquake? Will you take plastic, or cash, for that hotel room a county or two away? Bigger disaster? How much for enough gas to GTFO of Dodge to another state? Let Visa and Mr. Greenback solve that problem.)
And it also works for ordinary travel. Like when the 60-IQ @$$holes at one bank cleverly decide that when you travelled, you stole your own card, which was why you bought the tickets in your own name and used your own PIN number with it, and they put a lock on it, and it's midnight Friday ten states away when you find out, and no one answers their Customer Disservice Line until Monday morning. But everyone takes crisp new $100 bills, and the card from your other bank account (which you got for just this sort of jackassery), from sea to shining sea. Ask me how I know.
But he left out the towel from Hitchhiker's Guide To The Galaxy!
Seriously, those are the absolute Minimalist Five that will solve almost every problem.
A variation on the backpacker's Ten Essentials is also a good idea.
A water bottle with a base-nested metal drinking cup solves several problems at once: water supply, canteen, drinking cup, cooking pot.
So does including water purification tabs or iodine crystals (Polar-Pur) in that first aid kit.
You should always have a power bar or granola bar handy, and probably something like jerky too, and a packet of cup-a-soup, plus tea/coffee/sugar/cocoa.
I've gotten through marathon flights halfway around the world and cross-country bus journeys on a bag of banana chips, and a bag of peanut M&Ms.
A flop hat/wool beanie combo and emergency rain poncho take up little space.
Neither do a sleep mask and ear plugs.
Sunglasses, sunscreen, bug juice, and lip balm will stop a lot of misery in 24 time zones.
And I've never heard of anyone getting stopped for carrying a map (get a large-scale one on waterproof plasticized vinyl rather than paper, if possible -- if not, put Stormproof on a paper map)of where they're going, and a compass. Most all of that fits in jacket, shirt, and pants pockets, if you wear cargo pants, or else into a chest- or fanny-pack go-bag.
Also, you can carry scissors: just make them the blunt ones, in the also-carried tiny pocket sewing kit, with a couple of needles, a card of assorted thread, and a few buttons.
And check destination and carrier regs, but you can usually even carry a Swiss Army Champion most places, if you grind off the 2 actual knife blades, which still gets you the other 15 handy tools.
And you should have already replaced the laces on your footwear with paracord. (Yes, even your dress shoes. If necessary, get the smaller gauge cords, which are still stronger, handier, and last longer than the OEM laces.)
Also, one SF secret out of the bag is their mini-survival kit sandwiched between their uniform's US flag and the Velcro attaching layer. You can fit some worthwhile things in a Velcro-backed patch on your gear that isn't a US flag (For a less terrorist-target choice, try a patch of the destination country instead - as long as it isn't Israel), and that won't set off any metal detectors. And you should.
For the dedicated, a decompression needle will fit inside the case of a gutted Epi-pen. (Ask me how I know.) Due diligence, but as both are medical gear, not weapons, you might want to give it a shot.
An assortment of zip ties can turn that rain poncho into a shelter, umbrella, or what-have-you, and solve other problems as well. Or putting tamper-proof closures on your luggage zippers while your out of the hotel.
Obviously, a big pair of the #175 pounders gets you non-metallic handcuffs, or a bombproof gear lashing. Like clipping something important to a car. Or a liferaft. Or closing the handle on a broken piece of luggage.
Two small ones and a bit of a stick will make an ad hoc toggle closure for clothes, bags, etc.
Let your mind wander for 200 other uses.
And you can add one or more of the small o-ring sealed metal screw top pill bottles to your key chain without anyone taking much notice, to carry personal meds, and the usual tylenol/ibuprofen/immodium/benadryl/dramamine sorts of things that should go with you everywhere. I've had as many as four hooked on with my everyday keys, and no one, from airports to courthouses, ever checks them.
Ditto for the 1½" $5 housekey knife blade on the same ring. Coast to coast, dozens of security checkpoints, never even noticed.
A bigger key ring pill bottle will hold USD $8.25 in new quarters, which is also about $100 if they're "junk" 90% silver, and over $11,000 worth if you stuffed it with 1/4oz gold eagles instead.
(It also works as something to give you a healthier closed-fist punch, while not getting you felony levels of brass knuckles trouble. Just saying.)
They'll also hold matches; fishing hooks, weights and line; or Vaseline-impregnated cotton balls, and you can get multiple colors that make them look like zipper pulls on carry-ons and such.
If I could get someone to make one only about 1/4" taller, you could get 10-20 US-sized currency bills in one. As it is, if I fold the bills a bit, I can still get 5 bills into one without much trouble.
Jellied alcohol hand sanitizer does that (which is a must for airline trips - passenger jets are mega-nasty, and seldom cleaned properly), and it's also a wonderful emergency fire starter.
But for just five things, he pretty well nailed it.
The secret to a happy life is comfortable shoes.