So, for the car/truck it seems like there is fair agreement on (re: emergency extrication):

* something to cut with (knife, belt cutter)
(I prefer a knife since you can cut smashed laminated glass if needed)
* gloves
* fire extinguisher
* something to break windows with (punch, crow bar, etc)
(I prefer a crow bar since not only can you smash, but you can pry -- stuck door, etc)

I'll add:

* flashlight

The suggestion for eye protection seems good as well.

And everything should be secured so it doesn't fly around in a crash.

Another thing is that I'd suggest your items be within reach considering you might be pinned in place in a crash.

-john