Jackie, it sounds like you need more storage in your truck. You must be ready for anything!
As for my own truck:
Fuel filters and filter change wrench
Laptop (both for driver logs and diagnostics) with Printer and 100 watt inverter
Winter Survival Kit (required in Illinois during the Winter months) which has blankets, water, extra food, work clothes, hat, gloves and 2 barbecue lighters
12v Electric Defroster/Heater/Fan
Fuses and Bulbs
Jumper Cables (soon to be replaced with a booster pack)
White Lithium Grease
Lucas Red and Tacky Grease (for U-joints, 5th wheel and driveshaft)
Lucas Gear Oil
Windex/Invisible Glass/John Deere Glass Cleaner
Brush, Broom and Dust Pan
Extra coolant, water, Power Service Anti-Gel, Oil
Crowbar (for repairing light damage)
Shop Rags and Towels
Sockets and ratchets (a set of standard and metric)
7/16 wrench (has a multitude of uses on my truck such as brake adjustment, etc...)
Cordless Drill/Driver with Lithium battery pack
Nuts and bolts
I DO NOT (HAVE TO) CARRY:
Air tools (Grinders and Sanders)
Spare alternators, sensors, brake parts, wiring or hoses. There's already limited space in my truck with what I already have and most of the time, my truck is fixed at the Company Terminal, where additional tools, parts and a full-time mechanic are available to assist me with anything I need.
It's not nearly as much as what you carry, but I have to make sure there's room for my clothes and possibly a passenger, plus my application is extremely weight-sensitive (I pull hoppers and heavy dry vans that make me weigh 75,000 to 82,000 lbs).