What's in your trunk?

[74/171FAN]

Air, along with garbage.

Pretty much. This, plus a bunch of random crap that isn't worth naming in full. General categories include books, clothes, shoes, random papers, vodka, and important car stuff like jumper cables and a tire inflator. I need to clean out my car because I plan on camping it in this weekend, which is much more comfortable when there's room to put the backseat down.

That sounds similar to my car (minus the vodka).  I do have a first aid kit back there though because my mom mandated that we all have one a Christmas or so ago.

[Dr Frankenstein]

Trunk: A sleeping bag, blanket, jumpstart cables, oil, coolant, spare wiper, doughnut tire, lugnuts + socket, jack, shovel.
Glove box: Local maps, napkins, salt and pepper, plastic ustensils, car reg and insurance, 2 FM scanners (A super old one (from a time when it could brag about being programmable) with 10 channels that I use for CB, and a newer one (200 channels) that gets better signal but doesn't support CB.)

EDIT: Added the shovel.

[Brandon]

Having a hatchback, I don't have a real trunk, per se, but...

Donut spare tire
Jumper cables
Flashlight
Tire iron
Tire jack
Ice scrapers/snow brush/squeegee
Golf umbrella
Thermal blanket

I keep other things in the side pockets, center console, and glove box:
Gas book, maps, towels, first aid kit, tire gauge, swiss army knife, leatherman tool, owner's manual (why people take this out of a car blows my mind), umbrellas.

[realjd]

Spare tire, jack, etc.
Flares
Reflective triangle
Jumper cables
Golf clubs
A couple boxes of golf balls
Fold up windshield screen

In the summer I'll often have a swimsuit and towel back there as well.

[Duke87]

Trunk: big box of CDs, a quart or so of motor oil, combination air compressor/tire pressure gauge, ziploc bags, a few bottles of water, a couple of thin emergency blankets, a bunch of maps, unused handouts from my 2011 New Haven meet, an old pair of sneakers, and some random other garbage

Back seat: ice scraper/snow brush, snow shovel, tissues, a bunch of other maps, five quarts of motor oil and an oil filter awaiting my next oil change, an empty bag from Sheetz, and probably some other trash too

Back seat compartment: SEND HELP sign, a bunch of maps, and a tube of touch up paint

Glove compartment: registration, insurance card, owner's manual, receipts from a few servicings, the window sticker from the dealer that shows fuel economy

Passenger seat: notebook where I keep track of my mileage and fuel purchases

Tray between the front seats: flashlight, safety goggles, cellphone charger, parking receipts from various places I've traveled, and a bunch of change

Compartment between the front seats: wet wipes and there might still be a half eaten bag of pretzels which must be over a year old at this point. I rarely look in there.