Tool Kit

This. Or tough wire cutters. If you're going tanker, the single most important tool you need is your wire cutters. All the shippers seals are braided steel cable, and you will use the cutters or a mini bolt cutter EVERY TIME you deliver.

 

A tape measure if you are flatbed. You don't want to find out how tall that load is the hard way.

Dish soap is great to have around. A drop or two in a spray bottle is good for cleaning anything or finding air leaks. Takes the grease out of clothes. Cleans the road grime off the windshield so you don't get that glare from oncoming headlights.