seriously, what you should have
For those of us who have some mechanical knowledge of the cars:
a couple screwdrivers, flatheat and philips
a small socket wrench set (cheap bin at most parts stores)
a bunch of fuses
a cell phone
AAA or some sort of roadside assistance (my insurance gives me that)
a can of fix-a-flat (for those of us who removed the spare for a subwoofer)
When I was in Seattle, I happened to work next door to a euro car mechanic, and when my ground strap came loose, or one of the many times my Alt bracket broke, they would let me borrow the tools I did not bring with me, but when you really get stranded, nothing beats a cell phone and roadside assistance.
I also started carrying a spare alternator belt, a funnel to fill the coolant if I needed it, a cheap, somewhat light weight floor jack (just in case), mechanics gloves, and a lot of wet naps to clean up.
But now, with my 82, I guess I might be getting old, because I only have fix-a-flat and my cell phone and try not to venture to far out of cell phone coverage, just in case.