Ok, here's my contribution to more woodworking set of topics:

We just had a thread about favorite tool, here's the alternative:

What tool did you buy, that 1) you never used beyond once or twice or
2) ended up being worthless and you kept it anyway.

Here's mine:

Years ago, I bought a guide for cutting sheets of plywood. Cost me
over
$100 and I only used it once. I still have it.

Your turn.

MJ