This might not be the intention of the question, but DASHCAM. If you don’t already have one, get one.

There’s so many good reasons to have one. DON’T get the cheapest $30 one you can find on eBay. It’s a safety device, so go with one that has video reviews and has been around for at least a few years.

Make sure it mentions using a super capacitor instead of a traditional battery. Batteries will swell and quickly lose life and even potentially kill the camera in the heat.

Get something at least 2K resolution to be able to read license plates at a reasonable distance and test it regularly. I’ve had a previous camera show that all that good and recording only to discover half the footage was being corrupted.

If your car allows for it, get one that has a built-in rear camera loop for rear-end accidents as well.

Here’s the brand I’ve been using for a couple years and have had excellent results: https://www.viofo.com/

In my glovebox:

• Driving gloves (lol)
• Tyre pressure gauge (I don't have TPMS)
• Service booklet

In the cabin:

• Dashcam
• Phone holder
• Sunglasses

In the boot:

• Jumper cable
• Space-saver wheel
• 10" 250W subwoofer, 4 channel amplifier, and 6x9 speakers

Should be obvious but you should have tire repair stuff in your car. Especially since no one includes a spare tire kit anymore.

I got a tiny Harbor Freight air pump I keep in my car. It saved my ass on my last road trip when I ended up in the middle of absolutely nowhere with a tire pressure warning on. Stopped every couple of hours to air it back up until I got to the nearest Discount Tire on my journey. I also keep a tire plug kit!

Eehhhh .....

• water/packets of juice
• swiss army knife
• rope
• tow cable
• jumper cables
• tie-wraps
• velcro
• tape
• wd40
• 2 mugs
• binoculars
• candles+matches
• couple of plastic bags
• dog treats
• blanket
• rainjacket
• winter jacket
• scarf & beany
• toolkit
• toiletpaper
• solar rechargable flashlight
• mini compressor
• straps
• penci & paper
• axe
• medical kit
• spare bulbs of all kind
• assorted spare fuses
• .....and all the rest I forgot to mention

(No, i don't drive around in a box-truck ;) )

Dashcam was a damned good suggestion. I'll add first aid kit, blankets (if you get cold weather), and signal devices like road flares, reflective signage or small traffic cones. Maybe a few bottles of water and calorie-dense snacks. Just remember to consume and replace them periodically.

I keep a bunch of tools on hand because of work but tools are usually one of those things you accumulate over time as they become needed. A good start would be a socket set and a bit driver. Maybe add a breaker bar and a "stubby" driver or 1/4" ratchet for tight places. 1/4" "security bit" sets usually have some flatheads, PH1-3, plus a range of hex and torx bits with the little dimple because "security." A bit driver handled all the fasteners when I replaced my tailgate handle and my interior passenger door handle.

A tow rope and jumper cables are both things that others can use to help you should they not have their own. I know I like it when the person I'm jumping has their own cables ready. My own are usually buried in the compartment under my rear bench, which itself is often buried under toolbags and such. I also keep a couple square-ish off cuts of 2x6 in the bed which make good platforms for a jack/jack stands. You don't usually get to pick where or when you're forced to change a tire and jacks tend to sink and lean in soft earth without any support to spread the weight.

EDIT It's a real late edit but I still don't see it mentioned and it reminded me of something else too.

Thing the first: Fire extinguisher.

Thing the second: Some sort of mounting bracket it for it. Some will attach to a pillar, others might be made to reuse the bolts at the front of your seat mount. Wherever your fire extinguisher goes, it needs to be secured. Same goes for tools and other items which could become projectiles in the event of a collision.

It's a work truck so quite a bit. Full set of tools, including powertools, hardware and some lumber.

However, to actually answer your question: blanket, some warm clothes, hi-vis vest, 5 litres of diesel, common hand tools, socket set, flashlight, charging cables, baby wipes, a hatchet and a tow and recovery rope.

Wrangler or MX-5? Cause the kit is wildly different lol

Change of clothes
Blanket
Jump Box
Phone charger
Sunglasses

I have sometime similar to this setup myself.