Music
I'm the last wave of Generation X, and as is true for many of us, music has all but defined who I was at any given point in my life. I've been a goth, a mod, a rockabilly, an indie anglophile, a musical theatre nerd, a hipster (if you say so!), and an obsessive fan. I have a formal background in music too, having studied music as a violinist, cellist, and singer.
My knowledge of this genre is encyclopedic. And I've been so fortunate to have copyedited a number of books about bands or musicians I've loved forever. The Smiths? Joy DIvision? Someone pinch me!