In Marvel comics, Thor's legendary hammer Mjolnir is famous for being able to be wielded only by the worthy. For the unworthy, i.e., literally everyone except Thor and the odd someone else from time to time (a handy loophole for writers), Mjolnir simply cannot be lifted off the ground.
It is this property that electrical engineer Allen Pan, aka Sufficiently Advanced on YouTube, decided to replicate in his very own take on a "working" Mjolnir.
To make the hammer immoveable, he decided that strong magnets were the best method. Inside the head of his Mjolnir, he packed a microwave oven transformer electromagnet, which uses electricity to produce a magnetic field. This creates a very strong magnetic pull, strong enough that the hammer, when placed on a metal surface (that can't be lifted, such as a locked manhole cover), feels too heavy to lift.
The handle is attached to a capacitive touch sensor, which in turn is attached to an Arduino Pro Mini and a solid state relay, which serves as a switching device. As soon as someone grasps the handle, the electromagnets switch on, attaching the hammer to the metal surface.
However, the hammer can be turned off via a fingerprint sensor keyed to Pan's thumbprint. When Pan grasps the hammer, the magnets switch on. When he moves his thumb over the sensor, it switches off again, allowing Pan to lift the hammer.
Pan took his invention to the streets of Venice Beach, California, where he challenged unsuspecting passersby to lift it. It's a magnificent prank... and, just like in the comics and films, there may be more than one who is worthy. Sometimes brain does beat brawn.
Now he just has to find a way to make it call down the lightning and return to his hand when he throws it...