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.
I always keep jumper cables in my car. Mainly in case of my own emergency, but I have used them to help others.
Jumper cables should be in every car. I’ve only needed them for my own car once, but I’ve used them probably a dozen times for other people.
I also carry a small extendable snow shovel and an extendable snow broom. A bag of sand or oil dry (or cat litter) for winter are a good idea as well, assuming you live anywhere that snows regularly.