You mean like accessories/misc **** other than the tools?
Gloves, rags/paper towels, ziplocs, sharpies, paint pens, lights (handheld and work lights), soapstone, magnetic trays, extra couple pairs of safety glasses, notepad, brake cleaner, loctite, tape (painters tape, ducttape, and we have this foil tape at work I like a lot), pickup magnets, and whatever organizers you want to use for your tools.
I also have a plastic file box with file folders in it that I use to keep my work orders, time book, and other paperwork items organized. That sits on top of the box, along with a laptop.
You can find a lot of the stuff like glove box holders, paper towel holders, and such at Harbor Freight or online.
That's what I can think of off the top of my head.