Just checking… I was starting to like you, and I needed to be sure… 
And it’s panache45 for the fabulous win!
Insurance and registration information
Jumper cables
1 gallon of water
First aid kit
Pistol
Sun shade
Duct tape
Swiss army knife
Empty gas can
Fuse assortment
Electrical tape
A jug of water
Skates and skate pads
Pack of Gum
Change
Spare oil.
Tool Kit.
CDs
Scissors
Golfballs (my brother in law left them in the car when he gave it to me… I have yet to remove them… 4 years later.
Absolutely nothing. The owner’s manual, and that’s it. Maybe a pen.
I used to have an old International Scout with no roof when I was young, and I guess I never broke the habit of not leaving anything in the car. Anything I need for my commute I bring in my computer bag.
In the glove compartment:
extra napkins from restaurants
hand sanitizer
tire pressure gauge
In the pocket behind the passenger seat:
pen, notebook, and a map book
In the trunk in a large Rubbermaid container:
jumper cables
toilet paper
first aid kit
a small bucket
a gallon of water
extra washer fluid (critical in the winter)
owner’s manual
on the dash:
sunglasses
in the glovebox:
CD case with various CDs
pens
pencils
nail clipper
napkins
scissors
leatherman knife
in the driver side door pocket:
hand sanitizer
altoids
under the driver’s side seat:
map book
in the spare change drawer:
spare change
in the trunk:
phone book
paper towel roll
towels
My regular crap/survival stuff:
Entrenching tool
Skinning knife
Steel toe boots
Hard hat
Umbrella
Blanket
Snow chains
2 gallon gas can
Tie straps
Tarp
Trail mix
Change of cloths
Lighter
Cigar clipper
Fly rod
Box of flys
Random Junk:
2 Christmas ornaments
Coasters
Cleats
Mouthpiece
Stopwatch
I figure I can live out of my truck if it comes down to it for a couple of weeks.
Glove box:
Owner’s manual
Registration & insurance card
Little bundle of cards for library, bookstore, shooting range, and such
Door pockets:
Maps
Console:
Lactase pills
Altoids
Pen & paper
Screwdriver, adj. wrench, adj. pliers
Work gloves
Bottle opener
Tire guage
Paper napkins, salt and pepper packets
Back seat:
2 large towels (clean up spills, use for “tablecloths” if we eat in the car, lay on ground for tire changing)
Umbrellas
Flannel shirt
Cloth shopping bags
Cheapo truck-powered compressor
Pickup box, sometimes:
Heavy, heavy jumper cables
Trailer hitch
Rope
Glove box: spare eyeglasses, sunglasses, sunscreen, binoculars, multitool, wire saw, hand lotion, mini-maglite, tire gauge
Console: flashlight, multitool, lighter, matches, wetwipes
Seat pouches: MREs, water, fire extinguisher, hard candies, a knife or three
Behind seats: bugout bag (clothing, supplies, etc), about a ton of crap
Bed-mounted tool box: tools, ammo, mini-tent, camping supplies, jumper cables, medical kit, more water
eta: I live in earthquake country. I try to always be prepared for a major quake.