Installation:

Copy textures and meshes folder & Thor.esp to your Skyrim\data directory.

The folder-structure should look like:
... Skyrim\data\textures\weapons\Thor\Thor.dds | Thor_m.dds | Thor_n.dds
... Skyrim\data\meshes\weapons\Thor\1stpersonThor.nif | Thor.nif
... Skyrim\data\Thor.esp

Make sure that the plugin is activated in startmenu | DATA FILES.
The hammer is placed in the forge-menu along with the Daedric-items.

If you don't have the necessary perk use the console (key ^) to receive the hammer, enter:
help "Mjolnir" 4
write down the displayed code and enter:
player.additem CODE 1
"1" = amount

OR

player.addperk 000cb413
to unlock the daedric smithing perk.

To uninstall the weapon just delete the extracted files.

The package includes 2 versions:

The "calm" one uses a minor lightning enchantment with a chance to knockback the enemy.
The normal version uses increased knockback chance and an shockwave effect on each hit.
You can edit the weapon in the Creation Kit for further tweaking, check out the screenshot on the Nexus.

Kudos to Wodenswolf who allowed me to use his photos for the handle texture, check out his great gallery: http://wodenswolf.deviantart.com

PS: Yes, it is not perfect yet...i'm new to the CK and i still hate texturing. There is a clipping error in the thirdperson idle but i'm too busy in RL
to add new animations and all that stuff...i wanted to raise the handle position a bit so it looks better in 3rd person but then it looks weird in 1stperson
and so on, i still found no way to add a random % for the shockwave, getrandompercent had no effect so i made a 2nd "silent" version - but tbh i think it works this way ;)

Thx & have fun!