Not saying you need all of this just some suggestions.
An extra pistol with spare mags and ammo
Spare prepaid phone
Good fixed blade knife
Flashlight
Poncho
Handwarmers
Lighter/waterproof matches
First aid kit, pack everything you can make use of according to skill level but not stuff you dont know how to use
Some paracord
20oz bottles of water
Duct tape
Superglue
Zip ties
Bandana has many uses
Some spare cash
Emergency cell phone charger. Self contained unit, energizer makes one, possibly others
Waterproof notepad
Pencil
Laminated street and topographical maps of your area
A complete change of durable clothes
Towel
Blankets
Fox whistle
Working gloves
Folding shovel
Leatherman
Jerky or protein bars
Jumper cables
Ac/dc power inverter
Small air compressor
Automotive battery jump starter
Fire extinguisher
Lug wrench
Jack
Fix a flat or tire plug kit
Tow straps or chains
Come a long winch or vehicle mounted winch
Flares
Automotive fuses
Tool kit- common handheld tools and wrenches, sockets, ratchets
Electrical tape
Gasoline
2 quarts oil
Gallon of water
Crowbar
If its cold weather, keep some insulated coveralls in there.
Some of this was mentioned before i got it posted but repetition never hurt.