Keychain and Pocket Tools

tools

For the keychain:
Soft tape measure
#1 + #2 screwdrivers (philips and flathead)
Nailclipper w/ file & hook
Meds in a capsule (normally people stash drugs in these, so beware if you show this off): Activated charcoal pills and purifying iodine tablets can fit in one of these.
Cigarettes in a capsule
Bic lighter / flint firestarter
Folding scissors
Box cutter (there are ceramic ones if a non-weapon is needed)
Car window breaker (for emergencies)
P-51 can opener: Tape the blade if carrying on a keychain. (Incidentally, this one is a conversation starter if the right people see it.)
Tweezers
Bottle opener
Bootable Linux USB / Ventoy with Linux and computer repair images: You can totally stick a tech support USB on a keychain and you might actually get to use it. Use a flash drive model which is likely to be weather resistant.
Safety pin for opening smartphone tray, plus spare SIM cards for other carriers
Keychain lights, red + white

===Pocket Organizer tools===
Cotton Bandana: can use as a mask or use pieces of fabric for wounds/fires
Folding Spork or tiny spoon
Toothbrush (break or saw off the end of the handle so it will fit)
Another P-51 can opener
Pen & Paper: There's waterproof paper now. It smears more, but as long as you let the pen ink dry it will keep much better.

Vaseline: has medical uses and also happens to be great firestarter fuel combined with fabrics (duct tape or the paper tape or a bandanna piece)
Paper Tape: good for medical, can use as bandaids for small cuts or can combine with other fabrics (leaves, paper towels, bandana) to make your own bandages.
Antibiotic cream, Hydrocortisone itch cream
Probably another thing of tweezers

Round 360 degree hacksaw "blade" (can wrap in a spiral around the paper tape for easy storage): This can let you do a lot of weird repairs.
Mini self-adjusting pliers: Now you can officially fix anything as long as the nut isn't too big.
Mini bike repair tools: There are full sets of these which can handle a lot of bike repairs. Inner tube and replacement brake/shift cables will probably stay at home.
Plier multitool

Mirror
Altoids tin with useful small stuff (sewing needle & "pomodoro" sponge & thread, tums, tweezers, etc.)

===Backpack tools===
A tomahawk or hatchet or both: You'll hear all sorts of shit about knives being the most useful tool, but hatchets get way more work done overall. Of course you'll want a knife too for the more knifelike tasks. (If you have a home base, a double-edged long axe is really useful, keep one end sharp and let the other go dull and only use the dull one for splitting wood.) The reason for carrying a tomahawk and a dull hatchet is the same as that two-edged axe: You can use a dull hatchet for splitting wood or digging, and save the other for 
A small shovel/spade.
Food rations: Nuts, raisins, chocolate
Folding mini stove
Water filter
a small pot or steel bottle w/ lid
Emergency Radio
Change of socks + underwear
There are some nice synthetic towels that are super thin but still dry well. They dry out quickly, too. Much better than a thick cotton towel.

... there's lots of people talking about this kind of stuff. I don't wear backpacks often, but it's clearly possible to pack a lot of good stuff while still packing light.