Flashlight, Water & Food
Cars can break down or you can run out of gas if you don’t pay attention. A flashlight will come in handy if it happens during the night, especially in the middle of nowhere. Nowadays though many people have smartphone in which you probably have a flashlight app. If you are stranded for an extended period of time, you can certainly use some water and food.
Money / Change
Have you ever forgot to bring your wallet? Keeping some money in your car can be useful when that happens. It’s also a convenient place to keep the coins/change since they are heavy to carry in your pocket anyway. Coins can be used to pay tolls or parking meters.
First Aid Kit
This can be useful when you get hurt outdoors.