Here's a basic list of minimum tools that you must have in your vehicle at all times before you hit the offroad trail:
Screw Driver - long, short, flat, phillips/cross head, etc
A set of hex / allen keys
Zip Ties, long and short
Full set of spanners from number 3 till number 22
Insulation Tape
Pliers
Blades
Working gloves
Crow bar
Tyre puncture kit
Vehicle jack and wheel nuts spanner
Wheel Chocks
Flashlight/ work lamp
Warning reflector triangles
Safety reflective vest
Mseal
Cleaning cloth
Rags to soak up oil
Multitool knife
Disposable gloves when working with oil/grease
Tyre pressure gauge
Additional optional extras:
Tyre Compressor
Hammer
Locking Plier
Bottle Nose plier
Piece of wood to support jack in soft terrain
Spares like: hose pipe, fan belt, assorted fuses, headlight bulbs
Teflon tape
Hose pipe repair tape
Metal welding putty like JB Weld
Funnel to fill oil/fuel
Large Knife
Axe
Jumper Cables
Ratchet straps / bungee cords
Tyre Valves - ideally Colby valves