Help Desk Hell
When I went out in the field as a software support tech at a gov't agency, had a user in the Director's office call frantically stating her mac was typing random numbers all on its own! We had just upgraded to OS X and all I could think was somehow she'd gotten into the Darwin kernel. I spent two hours and could not reproduce the problem. Let her a note to call me when/if if happens again.
I come in next day to her equally frantic message from 9 pm night before. "It's doing it again!!!" I go up to the office, and as soon as I walk in the door, I know the problem. She has a mac laptop plugged into an external monitor, but the laptop is open and she's using that keyboard. HOWEVER, she also has an external keyboard plugged in, and on the FLOOR upside down under her desk!! I sit down, and without touching a thing, tap the keyboard with my shoe. "Is this the problem?" She starts laughing. I unplug the external keyboard.