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.
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.