They're a distant relative of the IEC C13 lead, aren't they? Left unobserved, they'll breed at the back of drawers and the bottom of tool boxes, but have an uncanny ability to be somewhere else when you need them.
Interestingly, I'm sure there was a hearing aid one[1] in the magpile[2] on my desk, but it seems to have crawled off somewhere...
[1] Flat-blade tweaker with a magnet at the other end.
[2] Who else accumulates Precious Things? Maybe we need a Gallery thread...