Authenticity is obviously an important factor when discussing the hammers of Norse gods. Sure, you could purchase a fake hammer just like Thor's at any toy store, but with a little DIY magic, you can make something a lot closer to the deadly weapon used on the fake planet of Asgard.
Sufficiently Advanced made a replica of Thor's hammer that's impossible for all others to lift unless you're "worthy," a.k.a have the right thumbprint. Seriously, even if MC Hammer himself touched this, it wouldn't move. The Mjölnir replica uses an electromagnet taken from a microwave and a fingerprint scanner to make it impossible to move for everyone but its creator when it's placed on a metal surface.
Taking the hammer to the streets, the Sufficiently Advanced team proceeded to prank passers-by, with its creator telling each person who attempts to lift it they just, "have to be worthy." He then easily picks up the hammer to the surprise of onlookers.
Check out the video, and then maybe make your own hammer. Or don't.