Good suggestions all around. I carry most of what has been posted but need to get an IR gun. I also think that while its nice to be prepared, most consumables can be bought when needed. We don't boon dock so there is always a Home Depot/Lowes/Camping World/ Local hardware store fairly close by. I am frequently going through the tool box making sure I have not left out something I have used recently and taking things out I know I have not/will not use.
One point I have though, WD 40 is not a lubricant. Most of us know that but... do not use it on anything like bearings/bushings/electric motors/rotating shafts. It will seize them up. Some of the more mechanically challenged folks here may not know this.