What's your favorite myth?

Hunahpu-and-Xbalanque-Maya-Codex-at-Dresden

Not, like, modern misinformation on the Internet, but longstanding cultural myths, with characters and the gravitas that comes with being really, really old. Max Gladstone writes about his favorites at Tor. I'm a big fan of the origin story of the Maya hero twins Hunahpú and Xbalanqué, as told in the Popol Vuh.