In the Marvel comics universe, no one can lift the hammer called Mjolnir but Thor, because no one else is worthy of the power of Thor. That is, unless you are another worthy Norse god, like Odin. YouTube member Sufficiently Advanced built a real-life version hammer that only he can lift. The caveat is that it must be laying on metal for the trick to work.
The hammer is held down by an electromagnet. The creator can lift it by putting his thumb over a sensor that reads his thumbprint and breaks the electric circuit. It’s a hoot to see bystanders try to lift it! One guy notices the sensor and thinks he can beat it, but then it dawns on him that he doesn’t have the correct thumbprint. -via Digg