What have you been into in the past couple years? Right now?
When I was a kid, I loved Lego; more specifically a theme called Bionicle. I knew (or think I knew) everything about it for its first couple years, and it brought me infinite joy while I was into it. Eventually it was replaced by Star Wars for the next 3-4 years. I loved that to bits, priding myself in knowing all the obscurest facts about it etc much like with Bionicle.
I havnt been into anything for the past year or two; my love for Star Wars has died down, but I still enjoy it.