I bring a basically complete set of tools including the Cruiser specific items like a brass drift and hub socket. Some other good things to have are a breaker bar, and a TRE puller. I have a lot of old parts in the truck, like the wheel bearings and knuckle bearing that I replaced in a front axle overhaul. I also have a set of coolant hoses(especially the specific formed ones, fan belts etc. I am paranoid so I have coil/ignitor (except for the 80)and distributor/ignition parts plus a spare distributor. A spare set of spark plugs is good. For really remote trips like Dusy-Ershim I take a complete spare front axle, minus the housing and differential but including a set of brake soft lines, drain plugs, cone washers, knuckles, lockout hub and a spare hub/rotor. I keep both rear axle shafts on hand as well along with front and rear driveshafts with associated bolts. This summer I also took a tie rod/relay rod strapped on the front bumper of my 40. I have rebuild kits for the brake and clutch masters plus a spare clutch slave(Yes-I know this is the 80's section!)
Things I have actually used on my truck or a friend's:
Complete knuckle kit
Front short side axle shaft/birfield plus one other birfield
Rear short side axle shaft
2 "U" bolts
Caliper bolt (I've seen 3 back off and drop out, none on mine yet)
lug studs-given to 2 different people I didn't know
1 gallon of gear oil
coil to distributer high voltage wire (needed and didn't have-sucked!)
misc. wire to repair fire damage
Valve stems for tires-many
Diff cover cork gasket
rear axle seal
Several quarts of ATF for power steering for others, fortunately
Several tubs of grease
1 tube of blue RTV
Fuel filter (technically not mine, but I carry one now)
many fuses but mostly for other people's trucks
1-FJ40 steering arm
Brake fluid-I gave a full bottle to a dude in Moab and he didn't even say thanks, but then he was having a really bad day.
I don't carry coolant-water works fine in a pinch
I guess the point is, you really can't have too many parts/fluids on a long remote trip. My general approach is to do a repair and save all the usable old parts and throw them in my truck. The axle shafts have saved me once, and saved someone else once. Keep any routine service item like oil filters and fuel filters in the truck too. Field repairs are a pain, but having good tools and spares takes some of the hurt out of it. If you just do day trips from a central location you can cut way down on the spares you take along.