…that are not stock items.
Flashlight
Deodorant
Cologne
Sunblock
Hand Sanitizer
Air Freshener
The iPod and/or CDs
Headphones (should I decide to hook up the iPod on-the-go)
A deck of cards
Sunglasses (I only wear sunglasses when I drive, or very rarely – can’t stand them really)
Tire Pressure Tester
Shout
Rags
2 Bungees
Standard Envelopes
Pens
PostIt Notes
Mini Notepad
Pieces of paper, plastic bottles, and other junk also known as “trash”.
Baby wipes - I’ve no baby, but these things take the grease off your hands like a dream.
I’ve also got two historical treasures - one is a stone which I think looks like it’s been fashioned into a scraping tool and the other is a piece of metal I pulled out of a rock on the beach - something to do with Atlantis I reckon.
Note to self: Remove artifacts.
Gum
Wisk Broom
Variety of tote bags (to use instead of paper or plastic)
Insulated carrier (for perishables and frozen food in summer)
Granola bars (to stave off starvation)
Napkins, plastic cutlery
Baby wipes and hand sanitizer
Toothbrush just in case
A little money just in case
Telephone book for reference
Old magazines
Coupon holder
Umbrella and my old raincoat
and…most of the stuff mentioned by the OP
Sounds like you folks are shaving a few miles off each gallon of gas by hauling around a small mountain of extra junk. I guess you’re covered if you’re suddenly seized by the urge to drive to the Oregon Territory and homestead.
Knitting bag containing current projects.
My old “EJSGIRL” license plates that haven’t been renewed since 1994.
Snacks.
Several good books.
Two bamboo beach mats that have never been used.
Dog towels.
Canvas shopping bags.
Sunglasses.
A Pokemon stickedex.
Coffee supplies for my Tuesday night meeting.
A mask from Mexico made of carved wood, porcupine quills, snake skin and I think something from a goat…
I’m sure there’s more. :smack:
Stamps, envelopes, and pen. My apartment complex doesn’t have a mail drop box, so I go to a post office when I’m out running other errands. While I prepare my bills at home, mostly, it’s handy to be able to prepare things to be sent out at the last minute.
Books. Usually collections of short stories or essays. Handy when I have to go to an appointment or make a spontaneous visit to the barber and have to wait.
In the backseat currently are two plush dolls, a Woodstock and a Snoopy. Each is buckled into their respective seats.
In the trunk: a shovel, a couple of bottles of oil, a road emergency kit, a road atlas, a copy of Austin Powers on VHS (don’t ask).
Books or magazines.
A box in the trunk containing paper towels, leather cleaner (for my leather seats,) windex, a thrower and tennis balls for the dogs.
Kleenex.
Cnavas shopping bags that I always forget to use! 
Canvas shopping bags
Hand sanitizer
Flashlight
Tire pressure checker thing
Umbrella
Collapsible chair (for the kid’s baseball or soccer games)
Couple of pens
Pad of paper
Rags
Bungee cords
Length of rope
Map books
Pocket EMT protocol book
Better-than-average first aid kit (it’s come in handy a few times)
Cheap disposable camera.
Nothing like a photo of the accident scene for the insurance company or the police before the vehicles are moved to the side of the road.
Never had to use mine, but at least its there if I should ever need it.
An inflatable boat. I get more use out of it than you might think and it is a good way to pick up women as long as you know them a little.
Lots of tools- hammer, wrench, screwdrivers, vice grips, and I think my channel locks are in there too. Very useful for jury-rigging car repairs which I often do because my cars have always been 10+ years old (like the time I replaced a shredded piece of radiator hose with some copper pipe and hose clamps).
Usually some oil, brake fluid, etc (see above).
If it’s raining a lot, a lot of water in the leaky trunk.
My yoga mat is in there. That’s so that I don’t forget it when I go to the gym.
That’s about it. I don’t like to keep a bunch of stuff in my car.
An extra dog leash and the ATM card/endorsement stamp for my company’s bank account. I only ever needed those things in the car (the ATM stuff), so I keep them there.
I cleaned out my car a year or so ago and put all of the junk in bags in the garage, thinking I’d put it back when I needed it again. I never needed it again.
Towels
Light
Self Starter
Fluid Set - Oil, Coolant, Transmission
Portable Air Compressor
Socket wrench/Basic Tools
flashlight (both battery LED and hand crank)
hand crank am/fm/weather radio
fire starter log, firewood, small bundle of kindling, plus newspaper
knife with fire starter & whistle
7 gallons of clean water
2 ton truck jack with 4 stands
5 quartz of 5W30 oil
packing blanket
compass
barometer
woven “keep warm” blankets
mechanics sled
2 full changes of clothes, including light jackets, hats and gloves
2 pair of sandals
a kite with 1000’ of string
Katadyn water filter
cook stove
2 fleece sleeping bags
enough tools to be able to fix anything that goes wrong (srsly, its like a 280 piece tool set)
fix-a-flat
deodorant
lighters
usually have my mtn bike in the back as well (I drive a '78 Blazer)
Basically, if I have to scram, I can. Where I live, if the shit hits the fan, the faster you start to get outta town, the more likely you will be to actually make it.
I might mention that you don’t have either food or TP on your list.
Good luck! 
Something to eat with
Something to cut with
Something to make fire
A fire extinguisher.
A spare tire
One of those pay-as-you-go phones, in case I break down.
A small blanket made out of “space age” material that reflects 98% of heat back onto me, in case I break down.
Junk.
Box of tissues
Bottle of hand lotion
Umbrella
Work ID (in its special compartment)
Comb (stuck on the sun visor)
Cell Phone (it lives in one of the cupholders)
12-pack of CDs, for when radio reception gets sucky.
Wow, more stuff than I thought.
A Refidex. (Street map). Some plastic bags. Nothing more.