The big guy himself. Notice the glowing arc reactor on his chest.
Tony Stark (aka Iron Man) has an electromagnet embedded in his chest.. It keeps bits of shrapnel from reaching his heart: if the metal reaches his heart, he dies. The magnetic field prevents that from happening. Obviously, he has to wear it all the time. It's powered by
Tony Stark is a walking, talking magnet. Tony Stark is also the CEO of a huge company.
Practically speaking, Tony must have a ton of trouble with paper clips. (To say nothing of metal detectors and high-end medical equipment.)