Also, since actual bailing wire is getting hard to find, rebar tie wire at your local big-box store works just as well.

I did not include it in the list because it is always in my glove box and/or armrest console but a Leatherman-type multi-tool with the wire cutters and needle-nose pliers is essential. This, the channel locks and the 1/4" socket set are places I do not cheap out (and flare wrenches but I do not consider them emergency tools).