I'm a sucker for pretty much any type of myth, my favorite book from 2nd to 6th grade was "The Illustrated Book of Myths" that was in the school library but really beaten up because kids kept taking pieces out of it, I miss that book. It got me into mythology.
Norse mythology is one of my favorites, I used to hate Thor in Marvel because I had lore I wanted to protect. I think my favorite stories are always "Loki decides to try to trick someone or play a prank; does not go well; Loki tries to get out of trouble and makes the situation worse, Loki is threatened with death or dismemberment; Loki finds some way to fix everything." I think my favorite was when he turned into a mare, lured a stallion into a forest, and returned with the 8 legged one. I can't spell his name right now.
I love Japanese mythology too, my love of it got even stronger when I read Storm Dancer.
Greek and Roman is always great, I like Percy Jackson as well. It's not really great but it's so accessible and easy to read that I enjoy it.
The mythology from the pre European South American kingdoms are awesome too, I remember one story in which two brothers play the Aztec equivalent of basketball against the gods of death. One of them gets decapitated by a bat. His head reattaches. There are owls with knives. Perfect.
Annnnd I just found my childhood in book form...
http://www.discoverbooks.com/Produc...D1qbINrT0yzA51iQStu4UuztXVLHZ-dxoCTG8QAvD_BwE