I don’t like carrying a ton of stuff in my truck, but there are a few things that pretty much stay there all the time. Most of it is stuff I don’t think about until I actually need it.
Recovery gear is at the top of the list. I keep a recovery strap, shackles, and the basic equipment I’d need to get myself or somebody else unstuck. Hopefully I don’t need it, but when you do, you really want it with you.
I also keep a tire repair kit and air compressor. A plug kit can take care of a simple puncture, and the compressor lets me air down on the trail and air back up before getting back on the highway.
Then there’s the basic stuff: a small tool kit, work gloves, flashlight, headlamp, duct tape, zip ties and electrical tape. None of it takes up much room, and you’d be surprised how often something from that pile comes in handy.
I always carry extra water and some food, too. A trail run doesn’t always go according to plan, and a few extra hours out there can turn into a long day pretty quickly.
I also keep a jacket and some extra clothes in the truck. Mountain weather can change fast, and I’d rather have them and not need them than the other way around.
Finally, I keep trash bags in the truck. They’re useful for dirty clothes, wet gear, garbage, or whatever else you don’t want rolling around inside the cab. And of course, anything I bring onto the trail comes back out with me.
None of this is particularly complicated or expensive. It’s just the stuff I’ve found useful enough that I don’t want to leave home without it.