I paid an extra $100 for an upgrade to 8K ram instead of the basic 4K on the Apple II.
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.