Kat the neurotic list-maker has been busy....combined everybody's, even tried to group them...feel free to add to this reference list
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Walkie talkies (FRS 2-way radios)
Mini Mag-lite
3D Mag-lite
Q beam light (never know when you might need 1,000,000 candle power light)
LED flashlight
Spare batteries
Carabiner clips
Ink pen
Fuses
Hiking poles (Kat special!)

Tire deflators
air pressure gauge
tire repair kit
air compressor
air hose + tyre inflator (run from the compressor tank)
battery jumper / air compressor / portable power supply (like the Cobra)

Ratchet Socket Set - American
Ratchet Socket Set - Metric
Set of metric deep sockets
Small screw driver with bit kit
22mm full size wrench and stubby wrench
few sets of pliers
breaker bar
3' pipe

Gloves
20' snatch strap
20' - 30' -Tow strap/rope
Bridle
Shackles/D-rings/Clevis
Ratchet straps
Bungie cords

Various maps/trail books
Flares
Glow sticks
Snow & window scraper / brush (winter only)
Fold-up camping shovel
Small Gerber hatchet
SOG / Gerber /Leatherman multi-tool
3"-6" Fixed blade or folding / Bowie / Field or liner lock type knife
Spare radiator hose
Lockwire

First Aid kit
Bottle of water
Toilet paper
Paper towels
Shop towels
Binoculars
Life hammer
Hi-Vis/ Safety triangle
Blanket
Solar blanket
Garbage bag
Small bottle of hand cleaner
Disposable camera or camera phone

Jumper cables / Jump leads
Bottle Jack
Piece of wood to put under jack
Four-way tire iron /Gorilla Power wrench
Power inverter
Fire extinguisher
Titan exhaust jack

WD-40
Fix-a-Flat
1 quart of oil
1 quart ATF
Oil funnel

Duct tape
Electrical tape
HD zipties
Razor blades
Bottle opener / corkscrew
Velcro

Quick detailer
Plastic/tire dressing
Wax
Windex
Rags/towels
California duster or feather duster for some

Jacket
Socks
Sandals
Waterproof boots
Tarp


....and maybe a Barbie doll somewhere