In my quest to get the serial numbers for all of my camera equipment, I've included anything that has a serial number at all. This means that I've now noted the serial numbers of sewing machines, stereo equipment, TVs, VCRs, and printers.
The list of items that have serial numbers is almost silly. But it's one of those 'in case of disaster' things that we all should have, but usually don't. We also have things, like my Lego sets and our DVDs and CDs that should be documented as well. I'm considering creating a spreadsheet to store this information and then it will be backed up, off site and safe.