Note: The following article by Joe Costa was sent to me. I attempted to contact the author but was unable to do so as he did not appear in a search of the CIS database. I liked the commentary so didn't reformat into the usual list style.
Here's a list of most of the junk I carry in my truck when off-roading; some of it might seem unnecessary, but much of it has saved my butt in many an occasion.
Most of my gear is carried in a military "cruise box" which is basically a folding metal chest, which I have riveted to the truck bed. In it I have a milk crate which is lined which a large trash bag in which I carry all my "dirty" stuff such as oil and grease. I always have at least 3 quarts of oil, A large bottle of brake fluid, starter fluid, WD-40, one new bottle of Antifreeze. I also have a small grease gun, K&N air filter spray, White Lithium grease spray and a small bottle of propane gas and a torch tip.
The Milk Crate/Trash Bag approach has kept all that gunk from spilling into the rest of the box even after some intense wheeling. Tucked neatly between the crate and a wall of the box I have 3 extra large trash bags, a roll of toilet paper in a zip-loc bag, an windshield ice scraper, some 1/2" purple tubing I haven't found a use for yet, a "Pensacola Shovel" (Air force survival knife), an Entrenching tool (Army folding shovel, if you don't have one go out and buy one now!!) in its sheath, old pair of snow gloves, and a 2 1/2 foot long crow bar which comes in very handy as a winch anchor when driven into the ground at an angle. Needless to say a good sledge is needed for the job.
In an ammo can (the .50 caliber waterproof type), I have most of my spare bits and pieces, such as wire (lots 22 and 12 gage or equivalents), wire connectors (crimps, twists), emergency fanbelt, gasket sealant (I use ultra copper, VERY useful stuff, a MUST), Duct tape, extra spark plugs (The ones from your last tune up should be fine), spark plug wires, assorted nuts and bolts, safety wire (.032) an extra distributor cap. You should also add any part you think may cause you trouble on the trail (such as any frequently changed part). On top of that I have a 10X8 nylon tarp and 6 or so long, thick bungee cords. Tucked in there is also a small backpack with a signal mirror, waterproof matches, a whistle (a pen cap will do in a pinch.) a compass, magnesium match, space blanket (2 of them, a small pocket sized one and a stronger, larger one), some chemlights (light sticks), a candle, a spool of strong fishing line, some hooks, 12 feet or so of safety wire (same as in the parts kit, great for snares), a mini maglight, a survival book (don't laugh! Panic and lack of action are the main threats to your survival! A good survival book or even a favorite book is just the think to help you relax and take a more critical look at your situation.) Bradford Angier's Survival with Style is an outstanding book and very entertaining in itself; paper and pen (Sharpie clothes marker is very good as it is waterproof), chalk, thick crayon, to mark your trail, for both you or a rescue party to follow. (In emergencies only, lets not go tagging all over Mother Nature please.) All that and you still should have plenty of room left for any extras you might think to pack with you, such as water packets and camping rations.
One VERY important note here: If ever stranded off road always STAY WITH YOUR VEHICLE! this is the golden rule; chances are rescuers will find your vehicle before they find you, leave only in the most extreme emergencies! And make sure to leave a note on your vehicle given your direction taken, time AND date, and how many people are going.
In the box, I also have my tool box, a Sears 3 drawer type, which holds a lot of tools. I personally like the drawers style tool boxes, because they allow you to be more organized and also lets you find the tool you need much quicker than just piling them all together in the same compartment. My tool list is fairly extensive, with more tools than I would normally need, but here's a list of what I consider a necessity: a set of box end wrenches of the best quality you can afford (never skimp on tools, cheap tools will only give up on you when you need them the most, I recommend Craftsman) of the style your rig requires (S.A.E. or metric). If S.A.E. have all sizes from 1/4 to 3/4 inch; if metric all sizes from 8mm to 19mm. A socket set in the same range as your wrenches, also 2" & 6" extensions. A good deepwell socket set may be a life saver, but is not really mandatory (although I find myself using my deepwells more than my other sockets), Wire cutters, needle nose pliers, Angle Needle nose pliers, regular pliers, vise grip pliers (very useful things!), stubby Phillips and common screwdrivers, 6 inch Phillips and common screwdrivers, ball peen hammer, breaker bar (The same drive size as your sockets of course), wire crimpers/ strippers, scribe, 10" crescent wrench.
That should suffice for most mechanical needs, but I also carry several other size screwdrivers (Actually a whole set of Craftsman clear handle screwdrivers), I also carry just about every size socket from 4mm 1/4 inch drive to 1 1/16" 1/2" drive plus several extra extensions, 1/4" to 3/8" 3/8" to 1/2" adapters and an extra 3/8" ratchet. An extra wrench for the sizes I use the most such as 10,11 & 14mm and 3/8, 1/2, 9/16". I have all sockets in socket holders to help save time looking for sockets, I also helps to keep sockets from jamming between drawers and things get bumpy. With the pliers I also carry a 6" C clamp and 2 3" C clamps, a snap ring pliers (use it once and you'll swear it's a necessity). A safety wire plier is also very useful, but sort of expensive. In the top compartment goes a dial type torque wrench, a 6" mechanic's ruler, a set of jeweler's files, some thicker files (be sure to include at least one round file!), a hacksaw and some extra blades, two utility knives (one is fine), mechanical fingers (great for retrieving dropped nuts and bolts from under a hot engine), a center punch, spark plug gapping tool, A set of allen wrenches, a carpenter's pencil, mini jumper cables (2 6' lengths of 20 gage wire with alligator clips on the ends, make your own or get them at Radio Shack), a continuity light. You don't need to have all the stuff I mentioned, but much of it has come in handy many times.
Next to my tool box I have a full case of MRE's (Meals Ready to Eat) from my old USMC days, they have a half life longer than plutonium and they'll fill you with enough calories to run a marathon or to drag a winch cable from tree to tree in 3 feet of snow. (Nobody said they taste good though. I keep them for emergencies only.) On top of it all I have a set of jumper cables. Last but not least I also have a small hatchet in there.
That sums it up for my Cruise Box; it might also interest you that I wired an utility light I bought at Chief's to the lid of the box which I wired to the battery, so I can look into the box at night and it also provides lots of light for the truck bed and acts as a sort of hazard light. In the truck bed, around the tool box I keep my tow straps (2 of them one is 35 feet, the other is 6 feet long, which I also use as a tree saver for the winch. Both straps have hooks on the ends), a foot long 4x4 block of wood (to be used as a base for my stock jack), and my winch pulley. On the passenger side is 100 feet of extra cable with loops on the ends and two heavy duty clevis pins, a plastic 5 gallon jerry can for water (always carry at least this much extra water). I usually don't carry extra fuel unless I'm really heading into the boondocks for a long time, in which case I take a metal jerry can and the spout goes in the cruise box. (Don't forget the spout!!! get the unleaded type, because it will fit all tank types).
Also by the Cruise Box I keep a large trash bag, which I use to pick up any trash I find along the trail and to put my own trash in. I also have a pick handle in the bed, which is very handle for loosening taut straps and for other assorted prying jobs. In the cab I have a 5 cell maglight (Maglight is the best flashlight I have ever had, I've had this one for close to 4 years now). Under my seat I keep both Phillips and common screwdrivers, a 6inch crescent and an adjustable pair of pliers all of which often keeps me from having to dig into my tool box. I also have a fire extinguisher (Halon), a fluorescent work light (the lighter plug in type), a first aid kit, lots of extra fuses in the glove box. I also have Lev-o-Gauges on my door and on the dash to tell me just how close I'm getting to flipping (don't depend on a gauge to tell you that, use your common sense), a 1 million candle power search light and a 20 foot lighter extension cord, and thick leather gloves. I also keep a tire pressure gauge handy. Under the hood I keep a rag tucked safely away to help me solve one of motoring's oldest questions: where do I wipe the dip stick?
That's about it for all the junk I carry, it might seem like a lot of useless stuff, but all it takes is one time for you to see the real value of taking all this stuff with you. You can also add many other regular off road items to this list such as a High-lift jack, a 12v air compressor, CB radio, astro turf for traction, camping gear, color TV, satellite up link, pinball machine, whatever. If it makes you comfortable to have it with you, take it. One note on High-Lift jacks: I used to have which I took with me faithfully, but it hardly ever saw any use, but the time I did use it, it was the only tool that could do the job. You read about how it can be used as a winch, and its true, but its a very last ditch effort as you would have a much easier time with just about any other method of getting unstuck, a come-along will do the job better and they are fairly cheap. What happen to my high lift you ask? Well someone broke into my garage and decided that they liked it better than I did.