OK, so any Mopar guy worth his salt knows you always carry an extra ballast resistor around in the glove box.

But what other parts, tools, or supplies do you guys carry all the time (or wish you had) that has gotten you out of a tight spot while cruising around town or on a road trip?

What junk is in your trunk???

Ballast resistor, voltage regulator, alternator.

Plus an ECU. Had more than one orange box failure.
.

AAA membership card. plus all of the above, a couple of fan belts, and one of those flat plastic case tool kits that has a bunch of sockets, screwdrivers, wrenches, pliers, etc in them.
small jack of your choice, and the exact socket, extension [if needed] and breaker bar to loosen your lug nuts.
or just tow a small trailer with your [almost] complete tool collection...........

CELLPHONE and AAA membership

I guess - as Mom used to say - my guardian angel works overtime, but I've taken a bunch of 1,000-mile round trips in old Mopars with none of that stuff onboard.
(Hopefully I haven't just jinxed myself...)
I suppose nowadays I'd probably bring a ballast resistor and a few hand tools for a long trip, mainly because parts stores probably don't stock old Mopar parts.
I have brought cleaning supplies, though...so I guess at least the cars would be clean & presentable by the side of the highway

A "jump box" is always nice to have (or at least jumper cables).

On my adventure motorcycle I carry a jump box, a tire plug kit and a small air pump that will at the very least get you to somewhere other than stranded in the middle of nowhere. Funny thing about where we ride a lot down in Amish area in southern Ohio a hazard that I never thought about was horseshoe nails being spit off by Amish horse and buggies. Who would have thought.

AAA is such cheap insurance. I started daily driving a 16 yr old vehicle and signed up for peace of mind - I had to get towed twice in the first year! I used it again last fall to have my other car towed 1hr away to the storage facility. So 3 tows for what, $75.00 a year? Cannot beat it.

I don't even carry a spare tire and cell phones are worthless around here. It really heightens my anxiety level wondering where I'm going to get stranded and die from exposure.

I don't carry anything extra. I have an awesome mechanic.

When I ran the old Mopar electronic ignition, I carried a resister and the ignition box and a few basic tools Put a 100K + miles on several different vehicles with that set up, never put any of it on my vehicles, but sure saved a few others along the way.

My coupe has a Dakota throttle body EFi, I carried a spare ECU because I junked a truck that had a good one, and it didn't take up much space in the tool box with a few hand tools and quick fix generic fix it stuff I never used in nearly 100K miles. Don't even carry a spare tire. I do carry AAA & a cell phone

My "new" 49 has a few very basic hand tools, no parts, and no spare. AAA, a credit card, and a cell phone, going to need a roll back (4x4). I'm not going to be working on this one on the side of the road, too low to get under, no one is going to stock any parts, and probably few parts available at most pick a parts. No worries, they don't help anyway. I'll deal with what happens when it happens.

Back in the day I had a small box under the seat with a ballast resistor, ECU, one long plug wire, a rotor, and the handful of tools required to change those parts. I don't carry any of those parts anymore since I've upgraded to EFI. Now I just carry my cell phone and AAA card with me.

At least a gln of water. Some good rubber tape/clamps/sealant for any leaky hoses.
A leaking cooling system will go further then any empty one.
Tire plug kit/small 12v air comp.: AAA or such could be Hours Away at times.
Sure there are more.

Besides the AAA card, I also have a bin I use for camping stuff but its also super helpful to keep in the back. Tire air compressor, green tire slime, tire repair kit, water filter / life straw, butane stove, rope, lighter, utensils, paper plates, fire starter, bug spray, bandaids etc. A "bug out bin" if you will.

Quarter inch drive full set, a few wrenches, lots of ignition stuff because of quality these days, old take off belts, kit of electrical splices and some wire, fuses, jug of coolant or at least empty jug to get water from a ditch. Full spare and bumper jack. Oil.

All this talk about "junk in the trunk" made me realize how an argument of how the spare tire was or was supposed to be mounted in the trunk of a '69 B-body. IMO it was mounted (at least for me) with the outside of the wheel facing down so you could fill it with your junk in the trunk. It made a nice place to store even if it was just cleaning "junk" like your Simoniz Wax and some rags and a horsehair shoe brush and some black shoe polish to get that darn Simoniz Wax out of the organisol hood stripe paint. Funny how back in the day when they were new it was more cleaning supplies that emergency supplies.
I think at the most I took was tools, spark plugs and maybe points for the drag strip? Rarely roadside emergency stuff. How life changes when you and your vehicle gets OLD

Yes, plus ECU but without alternator. Too heavy. Jumper cables, duct tape, cable ties.

Yes, an alternator is way too heavy.

Don't laugh, here's something I did that actually saved me, I kept a set of brushes from one of my junk alternators in my onboard toolbox.

Does he ride up front or in back seat?