I’ve made dozens of tools over the years. It would be safe to say they are all equally valuable, as all were created when there wasn’t a tool available to do the job.
I’ve made tools to remove spring eye bushings for leaf springs and install new ones for heavy trucks. This was so I didn’t have to remove the spring to take it to a press.
I made a tool for checking and adjusting air brake slack adjusters.
I built a gage for checking the toe on my race car, but it can be used to check toe on any vehicle.
Along that line I made a number of tools to aid in setting and adjusting all of the suspension on the race car, camber, caster, square.
Dozens of jigs and fixtures, for drilling or assembly. Stands for spare engines and transmissions.
My tool box is loaded with modified wrenches and sockets. I have bought a number of wrenches just to be modified for a single job.
I built a cart for a suitcase MIG welder that also carries the argon bottle, and storage for a welding hood, gloves and leather coat, clamps, spare wire, consumables and nozzle dip.
I made a tool for holding L series cylinder heads for porting work, so I don’t have to chase it around the workbench.
Another tool for holding a Z strut and spindle for mocking up brake caliper adapters and cooling ducts, and checking wheel to brake component clearances. It also is useful for mounting a wheel for polishing.
The list goes on . . . .