This was a few years back, before I knew this was even possible, but a portable hard drive off of Amazon. Not only was it sharp on all edges, it was only programed to show the storage without actually having it. I spent an evening “moving” docs from a dying laptop, only to plug it in the next day two find a fraction of what I thought I moved over.

Also, a yoga mat that disintegrated when I went to do a plank. Just pressing my hands into it was enough for it to flake apart.