Even on days when I'm not at the dealership there are three tools that are always in my pockets when I leave the house to work in the yard or garage.
Like many farmers, I feel lost without a pair of simple pliers in a leather pouch hanging from my belt. A good pair of pliers is a mini-hammer, wire-cutter, zip tie-puller, speed wrench and a dozen other tools all-in-one. I've found myself slapping my right hip, wishing I had my trusty pliers, while at a grocery store, a shopping mall and even in church.
The second tool I won't leave home without is a mini-screwdriver. The next time you're at an equipment dealership, notice that almost every mechanic has a mini-screwdriver tucked in his shirt pocket. I'll bet I pull out my little screwdriver 30 times a day to open a plastic parts bag, dig crud out of a hydraulic fitting, align a teeny hole in a circuit board, pry loose a roller chain master link's clip...sometimes I even use it to actually remove a small screw. Many farmers carry folding pocketknives that perform many of the duties for which I use my pocket screwdriver. I think my wife would prefer that I carry a pocketknife when we go out for dinner---she says pocket screwdrivers don't look "right" when worn with dress shirts.
The third small tool I won't leave home without is my mini-flashlight. Flashlight technology has improved in the past 5 years so that the 4-inch long pocket LED flashlight I carry clipped in a shirt pocket or front pants pocket is as bright as the 3-cell Mag Light I used to keep in my tool box, and much handier than dragging a trouble light and extension cord along every time I have to peer into a dark niche or cranny. Even if I'm not working on equipment at the dealership, that little light is my best friend after-hours when it comes to peering under the lawnmower (or more recently, the snowblower), digging through my fishing tackle box, or working on my wife's car. Inside the house I find myself grabbing that mini-light to illuminate the back corners of closets when searching for lost socks, rooting around under my computer desk for a disconnected cord, or when finally re-wiring the light fixture my wife asked me to fix three years ago.
If I was a bit younger, I'd probably add a cell phone, especially a smart phone, to my list of "don't leave home without it" tools. But I'm of an age where a cell phone is a necessary evil rather than a necessity of life.