Single project/one time used tools

[vavet]

How about an engine block ridge reamer? It’s used to remove the tiny bit of the cylinder bore that didn’t get worn because the piston didn’t go that high in the cylinder. It makes it easier to remove the pistons. I guess I technically used it 8 times when I rebuilt the v8 engine in my old cougar.
I also have a timing light. I had one for the cougar and gave it to the guy who bought it. Then I bought a 95 f150 with adjustable distributor and had to buy another. I don’t think I’ll ever need it, but it has a spot in my toolbox. That’s one of those things that when you need it, you really need it. I’ll probably never have the opportunity to teach my son how to use it.

 

[fourjeepin]

Fuel injection test light kit. It was only $20 and in use for about 2 mins. It didn’t cost enough to bother with reselling and doesn’t take up much space, unlike drywall lifts and engine hoists.

 

[finn]

I am sure there is more but one tool that comes to mind, as the boiler just kicked on...
Is the $130 digital meter for measuring water column. Bought to adjust the gas valve on my DIY NG hydronic boiler install.
Used it once and have Zero regrets buying the tool because I saved over $10K by DIY than the lowest quote I was given. Learned a lot and if and when it quits I am confident I could get it running again.

I bought an $8.00 water manometer and requisitioned some food coloring from the kitchen cabinet to do the same thing.

Worked fine. In fact, we used water manometers until the advent of automated data acquisition systems in the 1980s in the engine lab.

A manometer never goes out of calibration.

 

[Renegade1LI]

Being an absolute tool ***** I buy tools I don't need, just to have them in case. Bought a HF pipe bender still haven't used it, but it's only been 2 yrs. 3 ton arbor press, restored & sitting pretty, ready to go, I could keep going but I love acquiring new tools & equipment.

 

[rust in the eye]

The Ford spark plug removal tool is one of those tools that's it's better to have on hand and not need it than to need it, and not have it Like a fire extinguisher in many respects. We have great luck with decarbing the engine then popping those plugs out with a 3/8 cordless impact.
On a side note, I'll get my *** kicked doing a certain job, discover that there's a tool to make that job easier, get the tool, and never get that job again

How are you doing it there?