Magneto-Grade Neodymium Magnets
I'm sure there are stronger magnets out there, but these tiny, 1/2" x 1/8" neodymium discs carry instructions to keep them away from children and not to use them as toys, so I'd say they have some pretty serious sucking power. Those warnings are two I'd heed if I had myself a roll of 10 rare earth Magnetos anyway.
The super strong manipulators of the electromagnetic field have a pull force of about 6.1 pounds and are rated magnet grade N48. See if you can get two to stick on either side of your palm or hold a deck of cards to the fridge without starting an impromptu game of 52 pickup.