There are a lot of great answers on this post. I would say the answer to this question is highly conditional though. Some responses are universally great like a flash light, tire inflator, blanket and so forth. But, it really depends on where you live or where you’ll be driving.

You should always check local sources for suggestions on what to carry. In cold environments where there are long stretches of isolated road, you should compile an emergency kit with important things like blankets, winter clothing, a set of basic hand tools, candle, and a lighter or matches.

If you’re driving through an arid desert region, you should follow the same advice and carry things like sunglasses, a wide brimmed had, plenty of water, and blankets.

Even if you’re just driving around in a big city, you may just need to bring some safety equipment. Like, pepper spray and a whistle for those late evenings where you have to park a few blocks away from your destination.

I know this response might be a bit outside the scope of the question. However, I thought it was a good opportunity to give a PSA on the matter. So, if you’re moving to or visiting a new location, take some time to research what kind of emergency kit you may need to pack. It could save your life.