Well, practically speaking, having too many tools on-hand won't help you if you don't always carry the replacement part with you.
So you can get the broken part off while stranded on the side of the road. Now what?
That being said, I keep some 'go-to' tools in my T4R at all times. Of course, I use these tools for work, too, but still. I also use them for random furniture 'trash finds' (A LOT of people throw out good furniture that can simply be brought home, cleaned, then resold on Craigslist for some good money).
I bought my main bag due to the absolutely perfect way it holds my Milwaukee M12 Drill and Impact Driver, as well as the higher AH batteries. The center pouch is actually meant for one of those tackle box style trays, but holds the drills perfectly. It was really 'Walmart impulse buy', but I think it worked out great.
In my main bag, I keep:
- 1 Milwaukee M12 Drill
- 1 Milwaukee M12 Impact Driver
- 1 6AH M12 battery
- 1 4AH M12 battery
- 2 2AH M12 batteries
- 1 set of 1/4" hex to 1/4", 3/8", and 1/2" square drive adapters (A MUST HAVE for car work, alongside your impact driver and extensions)
- 1 1/4" square drive Metric ratchet set with flexible extensions and extra 1/4" square to 1/4" hex adapters.
- 1 100 pc 1/4" Hex security bit set. This includes 4 hex bit holders for my drill/impact driver. (I need an impact rated set, but this one is holding up well, so screw it)
- 1 box of screws (usually drywall).
- A few different sizes of screwdrivers, both flat and Phillips
- 1 Small crescent wrench
- 1 small Needle-nose pliers
- 1 small 45deg Needle-nose pliers
- 1 Small vice grips
- 1 Lineman's pliers
- 1 Allen-head key set
- 1 Wire cutter
- 1 1/4" Hex head drill bit set
In my auxiliary bag, I have
- 1 Milwaukee M12 Fuel Hackzall with blades
- 1 Chicago Electric Reciprocating Multi tool with blades
- 1 3/8" Ratchet
- 1 10" 3/8" breaker bar
- 1 6" long 3/8" extension
- 2 3" long 3/8" extensions
- 1 Larger crescent wrench
- 1 Large channel-lock pliers
- 1 Pair Tin Snips
- 1 Large Needle-nose pliers
- 1 Set of plastic trim removers (like little pry bars)
- Custom 3/8" socket rail with 10mm, 12mm, 14mm, 17mm sockets, and a spark plug socket.
- Wrench set (10mm, 12mm, 14mm, and 17mm)
- Several more sizes of screw drivers
- Electrical tape
- Different sizes zip-ties
- box cutter
Too big for the bags, but I keep tucked between the wheel well and tool bags:
- 1 24" black iron pipe as a cheater for the 3/8" breaker bar
- 1 24" Prybar
In my passenger side rear storage compartment I keep
- 1 set Jumper cables
- 1 drawstring bag of ratchet straps (4 count)
- 1 Tire patch kit
- 1 cheapo HF brand compressor (DOES work if you don't mind waiting a while)
- Duct tape
- WD-40
- Small bottle of Simple Green (EXCELLENT for hand washing)
- Some paper towels
- Ziplock bag of different size hose clamps
In my glove box, I keep:
- Multimeter
- Small electrical wire adapter set
- 1 Spare spark plug
- 1 Spare MAF (well now, my old, possibly dead original MAF [still diagnosing it])
Between the driver seat and center console, I keep sheathed:
I use the standard stock bottle jack, and I think it works really well. I'm stock height, though, so YMMV.
If I'm doing real suspension work, I use my larger jack and jack stands, of course.
I also have 1/2" drive ratchets, sockets, etc, but I've never needed them while out and about. I really don't offroad much, being 2wd and stock height, so my 3/8" drive set works fine.
I work in IT, so I also usually keep a bucket of random monitor and network cables and adapters, as well as a network cable testing kit.
When I know 'll need it (cabling job, or some such), I can fit my Werner 22" telescoping ladder in the back. Simply fold down one of the seats and the ladder fits perfectly between the back hatch and the bottom of the folded seat. Less than an inch clearance. Like it was made for it.
I also usually have a small furniture dolly with me, both for large computer equipment, and furniture finds.
So my combination of tools fits mostly in 2 bags for easy carrying, works for everything I might need for work, on the road in my T4R, and any slight furniture disassembly needed to get it to fit in the back. I've also used them for some odd plumbing jobs around the house without any need to go to the garage for more tools.