An item that I think is an absolute must-have for an car emergency kit is a paper map (or even better, a paper atlas!). Even though GPS devices and smartphones have now become commonplace as the means for finding our way, technology still isn't 100% fool proof. There are still areas of the country that don't have cell service, and sometimes our devices can also crash on us. Reading a map is an excellent skill to have, and I'm so thankful that my mom taught me how to do this when I was younger! (Fun fact about me: I absolutely adore reading maps and atlases for fun as well!)
Two items that I also wanted in my own kit were a lint roller and an adult coloring book. You never know when you might be in a sticky situation with your clothes and want to clean up a bit, and as far as a coloring book goes, you also never know when you might be stranded somewhere and need fast and easy entertainment!
Lastly, I've heard before that some people keep bottles of water and perishable food in their car's emergency kits. Here in the South, summer temperatures are often in the high 90s and feature extreme humidity, so I didn't think it was the most practically decision for my kit to keep food and water in there- I was worried about how long it would last! But if you are from a cooler climate, these might be excellent additions to your car emergency kit.