my outback toolkit
Having operated off a trailer all over the western USA, this is a subject dear to my heart! The toolkit is still evolving, but so far:
spanners (5/8 & 11/16? I forget), funnel, and pint of MR/TR gearbox oil for when you want to pull the chip detector all by yourself on an island in the middle of a flooded river 50 miles from cellphone coverage!
magnetic-bit multi-screwdriver (spare bits to replace those lost in the sand, please). AND tiny right-angle ratcheting slot and crosshead drivers, else you'll never be able to twiddle with engine cooling baffles.
at least all sizes sockets from 1/4" (clutch switch adjustment) to deep 7/8" (spark plugs). 7/32 and 11/32 will be vital for the 999+ engine baffle screws. 1/4" drive setup will take up less space & weight than 3/8; so you can carry ratchets, T-bars, various extensions, and universals in that size. And a Dictionary of Blasphemy.
Open-end & box-end in normal sizes weigh more, try for super-cheap pressed steel (they only have to function for a few minutes?)
Tiny open-end & box-end 1/4" through 7/16" are well worth having.
Needle-nose & plumber's pliers. Tiny wire cutters. Safety wire. Small tube of Silicone seal. Small tube of grease.
Tube of torque striping (consider matching color of the squiggles on nut heads emplaced by Officially Recognized Service Organizations).
Hacksaw (blade only?). Duct tape. Electrical tape.
You DO carry spare in-line fuses for the clutch wiring harness, no? Blowing your only fuse on above-mentioned island can ruin your day.
If you don't regularly compare your arm muscles to torque wrench values, carry one. IF you know the official torques!
How to carry: I put most of these in a couple of small plastic screw-top bottles left over from groceries. Light-weight, transparent, puncture-proof, waterproof, rustproof, unbreakable, instantly recognizeable. Properly loaded, they even float (remember the flooded river?).
OK, gang, what have I forgotten?