Greek.

Norse

The greek gods and stuff like that.

I am most familiar with Greek mythology, but I think all of it is fascinating to a high degree.

My own, Inuit mythology, as I find it most relatable.
(For a quick lesson, please see: link)

The ancient Greeks had some awesome stories. And though I have only ever gotten a small taste of it, I think Norse mythology is also pretty cool.

I also don't know if this would count as a "mythology" per se, but I enjoy the old tales of the Fair Folk. Y'know, the old stories of fairies before they became reduced to nothing more than Tinkerbell-esque critters in the public mind? Those stories kick ass.

For me, it's Native American religion and mythology. Like Stormy, I find most religious/mythological traditions fascinating.