I keep all of this shit in the back of my car, some of it is under the floor, some of it isn't. Gallery here, of some of the stuff:
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General Automotive
2.5 lb Fire Extinguisher
2 1/2 Ton Floor Jack
6x6 Wood block for shimming when jacking taller vehicles
4-way tire iron
Tire plug kit
Very nice dual cylinder air compressor
16ft 8 gauge jumper cables
Quart of BMW 10W30
4x 1L SmartWater bottles
Safety Glasses
N95 respirator
6x 15 minute road flares
3x 30 minute road flares
700 Lumen O-Light M30 Triton Flashlight
Two microfiber cloths
Microfiber diamond-weave drying towel
Griot's Garage Interior Detail Spray
Trauma Kit Contents
Seatbelt Cutter
Glass Punch
Bag Valve Mask
Range of various sized NPAs
Hemorrhage control (tourniquets, trauma dressing, clotting sponges, gauze, chest seals)
XCollar cervical splint
Saline rinse
Epinephrine auto-injector
Trauma shears
CPR mask
Non-latex gloves
Rite in the Rain notepad with Pen
Yellow and red glow sticks
In addition, I carry a full compliment of 72-hour survival gear organized into my Get Home Bag
On-Person EDC
Springfield XD-S 9mm
Leather SHTF Holster
Nitecore P12 Tactical Light 2015 Model (1x18650, 1000 OTF Lumens, many useful modes, gorgeous interface)
Leatherman Charge TTi
Waterman Hemisphere Fountain Pen
Autum Dualist Wallet (Powder-coated aluminum wrapped in Horween leather, handmade in the US)
VOID V02 Wristwatch
64GB Samsung Galaxy S6 Edge in Sapphire Black
Nite-Ize S-Biner with keys
32GB LaCie Flash Drive
Exotac Ferrocerium Rod and Striker
Fob for 2015 F31 M-Sport
Portland Bee Balm
Ray Ban RB8313 Carbon Fiber Aviators
BMW M Belt in Anthracite (Very decent $50ish leather belt made in Italy, marked up to over $100 because BMW knows enthusiasts/douchebags will pay the premium for that tiny embossed ///M logo).
Keen Flint shoes (good work boot/hiking boot hybrid, steel toe, low ESD.)
Sleep System/Shelter
SOL 5x7ft Utility Tarp (Orange for signaling, reflective inside for heat retention, ripstop, grommetted, actually surprisingly sturdy)
SOL Escape Bivy (Breathable, durable, warm to about 50F, I use this in the summer as my backpacking sleep system.)
Klymit Static-V Inflatable Pad (Whether crashing a friend’s house or sleeping
outside, I consider the insulation and comfort of a pad requisite.)
Mess Kit/Foodstuffs/Hydration
27oz Widemouth Kleen Kanteen (Single-walled canteens are multifunctional, and can also be easily used for cooking and boiling water, or warming your sleeping bag). 2x1L water bottles are stored in my trunk, so if I needed to, I could always grab spare water before setting out on foot somewhere.
The ever-popular Sawyer Mini Water Filter (There is really no reason you shouldn't have one, or five)
(3) ProBars (Calorie and protein dense, lightweight, easily packable)
(2) Paleo Jerky bars (the only grass fed/grass finished jerky I've found that
tastes decent)
(2) Trail Butters
(1) Lara Bar
Blend of Teas, Electrolyte Tabs, Coffee, Spices
MSR Titanium Fork and Spoon
Cold Weather Gear
REI Windstill Rainjacket/Wind-breaker (with integral hood)
Wigwam Merino Wool Socks
Marker Thinsulate Vest
PIG Gloves (Lots of dexterity at the sacrifice of warmth, great for protecting your hands when working on things)
Fleece Beanie
Electronics
Adam Industries Pitbull Monocular Night Vision Device (MNVD), built using the Gen 3+ Omni VI MX-10160C autogated intensifier from an AN/AVS-9. This was an incremental upgrade from my Gen 3 Omni IV PVS-14, and it produces an image that is less grainy and a tad bit more detailed/better contrasted.
Yaesu FT-60 Dual Band HAM Radio (Emergency communications, police/fire traffic, NOAA weather broadcasts)
Verizon Mobile Hotspot
PNY 5000MAh rechargeable USB charger (2.1A compatible)
UMX Android Burner Phone (disposable phone, prepaid card info and emergency contact numbers under the battery, charged up, and preloaded with useful survival manuals and Backcountry Navigator Pro with cached
1:24k topographical maps of my area)
ACR PLB-375 Rescue Beacon
Petzl Tactikka-XP Headlamp with red/blue lenses (replaced my Quark QP2L-X, as the hands-free functionality is very useful for setting up camp, working on a broken down car in the dark, etc).
Microsoft Surface Pro 3 Tablet (Core i7/256GB SSD/8GB DDR3/Win 8.1 Enterprise), soon to be replaced a Surface Pro 4 once they ship.
USB Micro Cable
Surprisingly decent bundled earbuds from my S6
1ft Ethernet cable
USB-to-Ethernet adapter for the tablet
256GB External USB SSD (in Ineo housing, with encrypted copies of critical documents/identification, as well as a bunch of my usual tech tools, for those impromptu "my computer has a virus" conversations at friends' houses, as well as our enterprise software and system images.)
Micro SD Card in SD Card Adapter
Tools
(4) MSR Groundhog Mini Stakes
100ft Blaze Orange Paracord and Spare Carabiner (mostly for guy wires and a center line to make an A-frame tent out of the tarp)
Spare Nitecore 18650 2600mAH Battery (for my EDC light)
Small Roll of Duct Tape
Roll of Electrical Tape
6 sq. ft. of Tin Foil
Zip Ties
Bit Kit for my Leatherman Charge TTi
Spare Dog Poop Bags
Zebra F-301 Pen
Rite in the Rain Pad
Cold Steel SRK Fixed-Blade Knife with Kydex Sheath (Such a great, sturdy
knife)
Spare 14rd Glock Magazine w/ 14rds Horandy Critical Defense +P Hollow Points
Firestarting
SOLO Butane Torch Extendible Lighter (Good for getting under tinder, burns fucking hot, and also great for cigars)
Waterproof Matches in Sealed Container with Striker Paper
Film Canister of Wax Soaked Cotton balls
Tea Light
Toiletries
Toothpaste
Compact Toothbrush
Tampon
Ass Wipes
Nail Clippers
Medical
Tactical Tailor IFAK
Epinephrine Auto-Injector
CPR Mask and Gloves
Quik-Clot Combat Gauze
Bitch Stickers (Band aids, gauze wrap and pads, etc.)
Benadryl
Mixed Aspirin, Zyrtec, Anti-Diahrreals (in the Advil tube)
Oral Rehydration Salts
Portland Bee Balm
Superglue
Bug Spray (100% DEET)
Sunscreen
Shears
ACE bandage
TUMS
2013 335i Msport Black sapphire/Coral red. MHD. stage 2--e30 VRSF DP, ER CP, Dinan Shockware. VRSF 12mm/15mm spacers. Cobra dashcam. Various codings. 
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