Thor's hammer, Mjölnir, is very special. It's was made by dwarves for Thor and it's really powerful. It can smash mountains, orcs and everything else in it's way.
Mjölnir actually means "That who smash" and that should paint a picture of what this hammer is all about. Smashing.
It doesn't matter if it's mountains, orcs or other enemies. Mjölnir will smash it.
When Thor throws the hammer, it never misses. Never!
And it always returns to his hand.
The Vikings were very fond of making Thor's Hammer Pendants. More than 50 Mjölnir amulets has been found throughout Scandinavia. Most of them are from year 900-1100.
So, if you find yourself in a situation where you need some extra strength and power, plus the protection from Thor, then Thor's hammer is the optimal pendant choice.
It's especially good to wear in life-changing situations, like when you start a new job, negotiating a raise (imagine Thor negotiating a raise. I am pretty sure he would get what he wanted) or dealing with difficult people.
Plus, it's a fashionable item with a cool story behind it :)