Being a keen 4WDer\camper the following are nearly always in the car.
car stuff - fluids, jump starter, recovery gear (straps, shackles, snatch blocks) spare ropes, other spares such as wiper blades, globes etc
tools such as spanners, screwdrivers, breaker bar, socket set, wire and wire clamping tool
first aid kit, epirb, portable uhf 5w and a couple of 1-2w
water tanks - 40L and 85L, water bottle filter (grayl).
fire starters - ferro rod, paper, matches, lighter, disposable gas canister blow torch, degreaser, metho,
bushcraft stuff - shovel, tomahawk, small block splitter, gas bottle, multi tool, saws, knives and sharpener, various cordage
insect repellent (a few types)
hygiene - soap and dish detergent, folding toilet and toilet paper (in a pvc tube), wipes, paper towels and regular towels
food related - auspit, lunch box cooker and gas cans, frypan, pot, plates/bowls/cups (solid and paper), cutlery and utensils, aluminium foil, some simple food (pasta/coucous and small tinned or foil packet tuna) spices, olive oil, hydralyte
shelter - tarps, ropes, pegs, battery drill and drill pegs, insect mesh and tent poles, inflatable mattress and pump, lightweight sleeping bag
torch, head torch, gloves x2 pair and I usually have a jacket kicking around in the back.
I often leave fishing rod, some tackle, small gaff and net in the car too unless I need to move it to put something else in.
other assorted stuff - webbing straps, electrical tape, gaffer tape, 75mm screw eyelets, batteries AA, AAA, D, 18650, CR123 and 9v
1L each of 2 stroke and bar oil, and chainsaw sharpener are stored in tub 24x7
chainsaw is in when I plan to get firewood or go away for the weekend OR when I forget to take it out.
When I go away I pack a few other essentials such as esky, chair, swag, clothes, toiletries, shower and instant hot water service, food and drinks.
If it's a long or extended trip I may take a few jerries of extra water and/or lifesaver jerry can water filter, and depending upon where I go I might also take some fuel jerry cans.
Also planning to fit out the trailer to carry additional water 250-300L, 2x 9L gas bottle, 3x20L jerry, fridge and esky.
