What is an item below 100 bucks that everyone should own?

For not much more, you can purchase a portable battery jumper. I've saved so many people without having to touch my car. I can move it between our cars, put it in my motorcycle saddlebags, use it as a PowerBank, so incredibly versatile. I'll never not have one moving forward.

Everyone? I have never owned a car, probably wouldn't come in super useful.