Truck Nutz is so obvious I’m surprised it wasn’t in the prompt.

Vise Grips

In a similar vein, I’d say my 1/2" drive CORDED impact gun. Just the thing for rusted-shut large bolts on the suspension, motor mounts, exhaust, etc. Not to mention it makes pulling wheels a piece of cake.

My lift. Now that I have one, I don’t know how I worked on cars without one. Rolling around on your back is for the birds!

Yup! I keep pigtails on all equipment so I can rotate a few chargers across many machines. 

My welder would be right up there on the list. Fixing things that you would have otherwise had to figure out how to make brackets and use bolts for and instead you just give it a zap is so convenient. Also I have made so many custom tools that make my life much easier when working with the welder. If you get serious…

Vice grips.  When all other wrenches won’t work a vice grip is there to rip it to shreads.  I currently own about 4 but it was one of my earliest tools.

Trickle chargers to keep the batteries charged in all the cars I might get to someday.

A mallet.

Two tools completely changed the quality of my wrenching
1) /4" cordless impact driver (like what you get in combo drill/driver kits)with a socket adapter. Speeds up the process of wrenching. You could swap this out with a dedicated impact wrench or powered ratchet, but this is very accessible due to the aforementioned…

For me, a heater. I live in the northeast, it gets cold and windy up here. I could wrench outside in my insulated onesie with a down jacket underneath, or I could pull into my garage, heat it up to 70* and wrench comfortably all day. Normally I only heat the garage overnight to 45* which is plenty to melt any snow or…

Youtube. 

The all purpose length of pipe. A bit of steel piping of indeterminate length and width. Use it as a level, a lever, a hammer, a brace, a long funnel, paint it yellow and pretend it is a lightsaber on Halloween, the uses are virtually endless. We all have one, and if we don’t we’ve all needed it and sworn when we…

WAAAM, an hour east of Portland, OR.

Took a Model T driving class last year, and I could not believe how much intense regular maintenance those things needed. I mean, don’t forgot to take apart the transmission every winter. Makes Harley Knucks/Pans seem like paragons of reliability.

No, you just need to walnut blast the intakes on any DI engine that doesn’t have secondary injectors instead

I think that the expectations of longer term reliability is near the top of this list. I look at the list of items that we expect to service during the life of the car in the 1980's that we no longer look at.

Overheating.  Yes it still can be a problem but its much less of a problem than it used to be.  The Grapevine in Southern California had all those signs warning you about the grade and overheating when I was a kid.  I remember my parents being nervous about the climb going to Frazier Park.  By 2000?  Hammer the gas up…

Bent, missing, broken car antennae.

Geez... where to start. Since it’s currently winter, I’ll go with cold starts. Back in the day when 100,000 miles was almost unheard of for a car, everything got worn out well before then. So on a day like today (it’s 0F where I am today) that meant that your car would prefer you just didn’t use it. If you wanted to,…