I used to carry a Victorinox Swiss Army Knife. It has multiple tools on it. Came in real handy for cutting tubing at the hospital. It has one blade of about 3 inches. Also has a handy leather punch that I use to add holes to my belt as I lose weight.
As a youngling growing up in the country, I tended to carry a pocketknife all the time. Less so when I moved to the city and NEVER at this point. I am deaf with a cochlear implant and while we could sit somewhere quiet and converse, I have trouble hearing in noisy environments. Given that I have to go explain to however is tending whatever kind of scanner for whatever security that I have a medical device, I think having even a little knife might cause greater confusion.
Deaf people get messed with a LOT and I don't want to give anyone a reason to bug me.
My grandfather is the reason I play guitars. He was a mechanic and a tool maker, could fix anything and could fashion a part or tool from scrap metal. He kept a 52’ Tele in his shed, mucked up by grease (his hands were permanently greased). Anyway he gave me his Swiss Army knife when I was a kid, I carried it for decades then TSA took it from me. Still upsets me, I almost ran from the gate I was that unhappy with them, but I had a 11 month baby with me. Quit carrying after that but I do keep a 16” kukri in my backpack.