Not necessarily unique, but I mostly always carry a small pouch containing a full D&D dice set.

I haven't needed dice in... years, now that I think about it, but I carry them as a symbol of luck. Not good luck or bad luck, just luck, chance. Helps me keep things in perspective when everything goes sideways.

I have the wallet of an old German conductor out of München Gladbach, Arnold Queasten. I found it in a thrift store as it looked like a nice quality leather wallet.

In it are still some notes from Arnold, on two of his business cards. A note of someone here knew from the war, and another person from the flute section.

There was one pfennig, a German penny still in it. So I have Arnold's last penny. I found his grave on findagrave, one day I'll visit that.

I'm now terribly afraid of losing the wallet, though, because I'm unsure a casual finder would appreciate the beauty of such a piece.

I've got a black joker card in my wallet. I was walking to the tram stop with someone once, when I saw this playing card face-down on the floor, so I said "bet you I can guess this card," I knelt down, and I said "I think it's a joker." I was about to turn it over when my friend said "hold on, black or red?" I said black and turned it over, and now it lives in my wallet.

I used to have a 1/4" nut that missed the threading process. I had it on my keychain to remind me that even if something is done millions of times without error, sometimes mistakes can happen.

Lost it when my backpack was stolen.

A crow-calling whistle and a small tin of peanuts.

My granfather's watch.

I keep ear plugs in my zip pouch wallet so I'm always ready for any concerts or random loud areas.

Made a 5" aluminum baseball bat in high school shop class learning how to use a lathe. It's been on my keys ever since. Thing is probably older than most folks reading this.

Edit: pic as requested. :) https://i.imgur.com/jrxStc4.jpeg

A metal red uno reverse card sits in my wallet. It was a gift from my girlfriend and an acknowledgement of our in joke of replying no u to compliments and I love yous.

Syringe of thermal paste

Small high power flashlight, about the size of a tube of m&ms. People laugh at it all the time, but it comes in handy weekly, sometimes daily.

Think of how many times you pull out your credit cell phone light. Now imagine being able to light up a room like daylight if need be. Very useful.

Those same people who laugh, eventually realize the value, and come asking for my light when we're together and it's needed

Leaving aside points about driving licence numbers being unique or whatever, it would be the silver pentagram that I made back in the '90s and have worn (or occasionally carry in my wallet etc, when the cord breaks) ever since.

A pack of nicotine gum.
I don't need or use it anymore, but I still carry it with me every day.
It's a reminder of how addicted I was and how I swore to never smoke another cigarette in my life.

My fingerprints.

Pink plastic heart and a marble in my pants' change pocket. My daughter gave them to me on two separate occassions when she was 2-3. She said "this is your heart" and "this is your sould" when she gave them to me and they've been in my change pocket almost every day for the last 5+ years.

An old silver pendant that used to be my mother's. It has a simple yet iconic design, people often notice it and make comments on it.

A set of keys that will open most of the doors in a certain national park. Turns out “government use only. Do not duplicate” doesn’t mean a whole lot to a crooked locksmith. My plan is to go test and see if they still work when I’m an old man. I won’t be surprised if they do

I used to carry a universal TV remote control with me. It's simply staggering how often it was useful.

At a certain point in time i carried a distinct coin with a scratch mark i made on it so i can flip it and see if i could make it fly (i was heavy into lucir dreaming at the time lmao). Its mostly influence from inception, u can get the same result from just counting your fingers, they look super weird in dreams😭

Nail clippers. Got them originally to help with a bad habit of cuticle picking, but I've learned they're weirdly useful. They can cut things in a pinch and no security check gives a shit about them unlike a pocket knife.

An arch lighter version of a zippo. It fits in traditional zippo cases so I have a collection of shells that I change out to fit the mood. The current one is matte black with a cthulhu theme in brass but normally I use the mercury glass with bones and flowers. My wife calls it my zappo.

Also the severed finger of an elf.

My ex-wife got me an engraved Zippo I used to carry everywhere, now it's mostly on my desk because I don't want to lose it at work :/

A tiny vial of peppermint clove oil. I struggle with sleepiness and lack of focus so after I've had an inadvisable amount of caffeine and am still not functional, I dab a bit right under my nostrils to help me wake up and focus a bit better

Also works as mosquito repellent on some species so if I forget bug spray I use some of this instead

Probably not super unique but a glass breaker/seatbelt cutter. If I'm in an accident or I come upon one, I want that ability with me.

Multitool

My daily carry bag always includes my Kindle, my cribbage board, and dog treats.