I carry a powerbank and various USB C adapters so if someone’s device dies I can help them out. It is a lot cheaper and smaller than carrying around seven different cables.
On top of that I carry Tylenol and bandages.
I used to carry a full first aid bag but kept forgetting to restock on supplies.
Snapblade 18mm razor, sharpie, blistex (superior to balm/stick in every way), bandages and alcohol prep wipes and triple antibiotic, Sawyer mini filter and a vacuum insulated bottle, and a towel - you never know when you’ll need a towel.
Oh also an extra mask, couple napkins, some new folded up tissues, and earplugs.