Mine - Its not that great but whatever - I taught myself a language through song translation.
I was heavily into German Rock music while I was in highschool, and I would translate the non-English songs for fun, with google. By graduation, I was almost able to speak the language. Not fluently, but I got by from the people I knew who actively spoke the language.
Its been 6 years and Im not even interested in the music anymore, maybe from constant repetition of the same 4 albums over and over.
Anyway, Whats yours?
Touch Typing.
A skill that will last a lifetime.