A Kubaton and handcuffs, just in case.
Great for you @MikeBKY but for most of us if we put handcuffs on someone we might be going to jail for the use of unlawful restraints (language might very but I am sure you know what I mean).
That’s why I do not carry them on my person. In the unlikely event I am going to arrest someone, meaning a citizens arrest, it is going to be a very big deal and I don’t take it lightly. And there is a very good chance they are suffering from recent case of lead poisoning but are capable of becoming a threat again. I am intimately familiar with Kentucky’s laws relating to arrest by peace officers and private citizens.
Israeli Bandage & Tourniquet. Other than that there are a whole host of “useful” items that are in every car I own. For Self Defense I keep my Tire Iron (L shaped one for the vehicle ) between the seat and the door or trans tunnel. Not a big fan of leaving “weapons” in my vehicles but there are places for them should I decide I have the need.
IFAIK, at least one rescue blade.
A fast opening liner lock S&W Border Guard knife.
Too large and heavy to carry comfortably, it fits in the glove box hidden under a road map.
It’s also cheap ($11 on sale at Big Five) but nasty looking,
4.1" tanto blade and a windshield breaker on the end
Just in case.
Two items in permanent residence in the car are a solar powered flashlight w/glass breaker & belt cutter (and other features), in the door pocket and an 8" dagger between the driver’s seat and console. There’s other stuff too, but asked for only one.
I don’t keep anything in glove-box due too my own immaturity @ age 19-ish.
But IF did it would be something small in caliber.
Tissues. Napkins. Pepper spray. Straws. Flashlight.
A couple different knives and high intensity flashlight. There may or may not be a laser pointer type thing as well to help visually incapacitate an attacker.