I carry my 40-year-old field service tool case (similar to
this one), plus a 3/8 socket set, and a large 250fp torque wrench for wheel lugs and hitch parts. I would turn around for any of those. I leave some tools permanently in the trailer, including the hitch-specific bar and speed wrenches, a prybar for when the hitch gets miffy, and a couple specialized Vise-Grips that I use to tighten hoses (and sometimes leaky packing nuts) on problematic camp bibbs. I also used to be religious about my high-pressure tire gauge, though with our new TPMS system I no longer need to be.