I would love to learn to at least read five of the earliest languages. Things like Sumerian cuneiform, Egyptian hieroglyphics, Sanskrit, ancient Greek, etcetera. Latin, Hindi, Arabic would also be nice too learn along with some type of Asian language as well.
It would be really cool to be able to learn early writing. Not sure what I would I do with the skill, probably think on it and write some sort of story. I mean, being able to read things from thousands of years ago. It would be a unique expeirence I would cheerish.