I bought a big set of broaches and bushings. I think I've used them once. But I don't care. I can't have peace unless I know I can broach.
I bought a Gorton grinder, fixed the bearings, and made a rolling base for it. Since then, it has collected dust. Really disgraceful, since it's probably the best drill sharpener on Earth.
I have a Veritas router plane, sitting in the box it came in. Not sure what it's for.
I like to keep my 8" rotary table on the mill, but my 10" table sits on a shelf. I'm afraid to lift it.
I learned how to use Fusion 360, and I used it to design an attachment that turns my 16x40 metal lathe into a wood lathe. I made the attachment, and I have never used it. Later I bought a very nice small Harbor Freight wood lathe and turned a Husky tool chest into a lathe cart. I have made one tool handle.
I'm not sure I've ever used my Dumore sensitive drill press.
I bought a mini lathe and converted it to CNC using a half-assed set of plans I found on the web. Not a great idea, unless you give up on the plans and get real balls crews.
On the other hand, there are expensive (or relatively expensive) tools that really worked out well.
The mill is an amazing tool. I can't understand why anyone would say a lathe is more versatile. A mill does everything a drill press does, better, plus a lot of what a lathe does.
I rarely use my plasma cutter, but when I do, I thank God I have it.
My dry-cut saw is a lifesaver. Zips through stuff that takes all day on the band saw. I use it constantly.
The 2x72 belt grinder is a wonder. Until you have one, you don't know how badly you need it. Cuts any kind of metal. Shapes. Polishes. Sharpens. I had to spend $500 on the body, and the spare VFD I used was a $300 item. Then I had to get a motor, a cart, and an enclosure for the VFD. I don't care. It rocks.
I put $300 CBN wheels on my bench grinder. Anyone who doesn't have CBN is insane. They last pretty much forever. You never have to dress them. They don't heat things anywhere near as much as ceramics. You can grind on the sides of the wheels without risking death. You never have to "ring" them to see if they're safe. You can grind anything under the sun on them safely; aluminum makes ceramic wheels explode.
Putting a VFD and bigger motor on the drill press was a great move. No belts to fool with.
Buying 5 angle grinders was smart. Don't switch wheels. Just reach for the other grinder. Getting a 6" Metabo with cutoff wheels allowed me to cut metal much faster than a band saw, and it even outdoes gas cutting and plasma sometimes.
I bought a Phase Perfect solid state phase converter. Something over three grand. I felt like a spendthrift, but it's fantastic. My big lathe runs like it should, and I was able to take the VFD off the mill.
I wish I had gone for a 7.5-horse compressor instead of 5. For most tasks, my compressor is a monster, but some tools really suck air.
The other expensive tool I haven't bought but should: lift that will pick up a car and also serve as a table. That would complete me.
I don't regret not falling for brands like Snap-On and MAC. Sometimes you have to buy the most expensive thing out there, but most of the time, you don't. If I had a $250 screwdriver, I would be ashamed of it.