Bicycle:

I had a large hole in a tire and had to walk my bicycle back over 5 miles. I now Cary a spare tube and small portable pump. I also switched my tires to one's with Kevlar banding.

Carrying a bicycle specific multi tool after trying to help someone on a trail.

Wearing full finger gloves after a fall without gloves gave me a minor cut up palm. The full finger gloves saved me when I got into a more serious accident later and a glove had serious road rash instead of my hand and fingers.

Blinking red light for bike and bag after a close call with a car.

Flashlight:

Before cell phone apps I used to EDC a mini mag in a covered holster. I needed a light when the power went out at work in a large windowless space. The head had turned and the battery was dead. I now keep a Pico light on my keys, a headlamp in my laptop bag and a flashlight app on my phone's home screen. I am always within steps of at least two of those three light sources.

Car:

After having the battery die in the middle of nowhere I picked up a battery jump starter. I charge it monthly because pressing the battery test button shows it drains enough each month to need a recharge.

Keys and spare alarm battery after losing a key and after having the alarm battery die in the winter.

Kitty litter after getting stuck on an icy Street.

When I used to have a full size rear wheel drive car I used to put a large bag of salt in the trunk to better distribute the weight. Anyone who has had the back kick out in the winter knows the feeling. I now won't consider buying a car without AWD or 4WD.

Rotating the tires every other oil change. If you have aluminum rims the tire can, (and did), seize to the hub. The emergency fix is to loosen the lug nuts and drive slowly a short distance. Rotating the tires frequently should stop this from happening.

Vacuum bag things you keep in your vehicle that can be damaged by a leak. After having a bottle develop a hole and soak my stuff I bagged everything except tools. It has saved me when it has happened again. Use Zip lock freezer bags if you don't have a vacuum sealer.

Cell phone charger. Not me, but too many people I know have said they had a low charge. $5 charger to not have this problem.