Two Flashlights
Because what if one goes out? What if it’s dark and you need another light source? What if you need a friend to help illuminate the issue? What if the batteries in one die?
These are all reasons to carry two flashlights with you in your truck. Don’t even think about using the little LED on your phone either. While those are useful in a pinch, relying on your phone battery for light in an emergency is quick way to ruin.