I guess it all depends on the type of trails you're running.
For the Hammers I typically carry this stuff.
Tools:
Wrenches, sockets, and ratchets to disassemble/assemble entire Jeep.
4 in 1 screwdriver.
1/2 air impact gun.
CO2 tank.
Tire plug kit.
Stock XJ jack.
Lug wrench.
Hacksaw.
big C clamp.
3 Lb. sledge.
Pickle fork.
Power inverter.
Haynes Jeep repair manual.
Spare parts:
CPS(crank position sensor)
Coil.
Fuel Pump.
Power steering hose(high pressure side)
Radiator hoses.
Ball Joints.
U-joints for driveshaft and axle shaft.
Clutch line.
Ballast resistor.
Quick connect fuel line fittings.
Front and rear axle shaft assemblies.
Rear drive shaft.
D30/D44 pinnion yoke.
U-bolt style yoke straps.
Cap and rotor.
a couple spark plugs.
Fuel injector.
Stuff to make spark plug wires.
Motor mount.
Large selection of spare bolts, nuts, washers, and screws.
Consumables:
4 quarts engine oil.
2 quarts diff fluid.
2 quarts t-case fluid.
2 gallons coolant mix.
1 quart power steering fluid.
2 small bottles of clutch/brake fluid.
Tub of grease.
WD40.
Brake cleaner.
Hand cleaner.
Spill-Tec absorbant mats.
Paper towels.
Zip ties.
Bailing wire.
Duct tape.
Electrical tape.
Fuses.
Recovery/safety gear:
Winch.
Tow straps.
Shackles.
Tree saver.
Snatch block.
Gloves.
First aid kit.
2 fire extinguishers.
CB radio.
Emergency blankets.
Flash light.
Probably a bunch of stuff that I forgot but that's all I can think of besides food, water, and beer.
Jes