I keep a pretty good setup in both vehicles, the truck carries a bit more than the car. I don't worry about breaking down myself but I like to help out when I see others in a predicament.
The truck box:

Jump box always charging on inverter when driving, internal battery swapped out for Clore JNC battery:

Bayco light on hardwired charger:

Top drawer has patching stuff, basic meter, ice scraper, gloves, battery terminal cleaner etc

Middle drawer is cargo management and tow strap

Bottom drawer has various lug nut sockets, breaker bar, 12 volt pump and other odds and ends

Can't see much in the bottom compartment but it's got a trolley jack, 20 foot jumper cables, 130 pc HF general tool kit, assortment of fuses, tarps and blankets.
In the bed I keep a 5 gallon Jerry can full of gas. I use Sta-bil in it but rotate that gas into my tank every few months.
Car has a basically identical setup, but with an empty gas can instead. HF jump box with Clore internal battery swapped in, also charging on inverter, folding drop light always charging, everything else is basically identical to what's in the truck.
It's mostly HF, but not all. Obviously used only very occasionally and each piece has served me well so far. The 12 volt inflators in particular are exceptional for the price and have proven themselves numerous times.