What's a good LEGAL tool/item to keep in my car for self-defense?

Lots of people in my area are getting their cars attacked on the road, while they're in them. I just want to follow the law and still protect my family (and myself) while in the car. Obviously I'll drive away if I can, but just in case I can't.

Edit: Sorry, I'm in the US, California.

Edit: [This](https://abc7.com/road-rage-man-with-pipe-tesla-assault/12695539/) fucking nut job lives in my area. He's not the only one.