When I was a teenager I used to carry a pocket knife. Never used it. Even when I got mugged. (3v1 and I wasn't about to escalate)
Now as an adult I carry a tiny tactical flashlight. Mainly use it for chores and work. FC13S $20. Solid purchase.
I hope I remember it has strobe mode that'll completely blind someone for several seconds. Would help to stop a fight or mugger. I keep it in the same side pocket I used to keep my pocket knife in...