Monitor Radiation
We had a user that insisted their monitor put out "bad radiation" and purchased disks to put on it, her phone, and who knows how many other things.
Amusingly, the radiation blocking disks were placed on the side opposite the screen, so if they blocked some sort of radiation, it would have probably bounced it back toward them.
After heartlessly ripping one apart, it "failed to come off the phone properly," I found that they were empty pucks of silicon.