The one I remember most fondly is the floppy drive/disk eraser we had for our TRS-80. Functioned perfectly as a floppy drive if you had it powered on BEFORE you put the disc in, and didn’t power it down until AFTER you took the disc out.
For a “bulk” instant disc wipe, insert the disc with the unit off, then power it on.
I never had a TRS-80, but someone who once worked at Commodore, gave me a complete printout of the 1541 floppy drive source code.
I remember noticing a comment that said something like, “if you ever end up here, you are in trouble”