Inspired by Thor from The Avengers, one man has built a real-life Mjölnir that is unliftable by anyone but him, so long as it's on a metal surface.
Mjölnir is the name of Thor's magical hammer, which in the comic book and movie world can only be wielded by "worthy" individuals. (The original Norse mythology is less clear on this, and people frequently attempt to steal Mjölnir from Thor. Dude needs to install a security system.)
Using a capacitive touch sensor attached to the handle, an Arduino Pro Mini, and an electromagnet poached from the transformer of a microwave oven, YouTuber Sufficiently Advanced created a giant hammer that only he can pick up. The hammer's creator then took his invention to the streets, tricking people into trying to lift the hammer.
Watch to see a bunch of confounded people really putting their backs into it, and the one guy who finally figured it out.