Notable appearance: Batman #584
At all times, Batman carries with him a miniature electromagnet capable of erasing any video tape or audio recording someone might try to make of him while he’s out fighting crime. This has made any footage of Batman nearly impossible to get, thus keeping his actual existence a mystery to the world. This little gadget first appeared in an issue of Batman written by Ed Brubaker that focused on a documentary film crew gathering evidence about whether or not Batman actually exists.
After realizing they actually got a clear shot of him, he took it upon himself to use the electromagnet to erase their footage, while probably killing their careers in the process. As the crew went home to their dingy studio apartments, Batman went home to his spacious mansion and billions of dollars. Justice had been served.