Just a small toolbox (which contains all I need to build the car), a few common size nuts, bolts, screws in a pot which lives in the tool box, cable ties, insulation tape, a few charged packs. That's it. If I am on foot or away from the car, I take some long nose pliers, box spanner, double ended screwdriver, in my pocket along with the spare packs and maybe a wheel nut.
Rich