Mine would be creating pen and paper ciphers for my made up secret communication needs.
Physical media collecting. Particularly if i have a functioning player for it. If i don’t then the interest goes down the drain. That’s why there’s a huge focus on books with me. Pulps. That’s why I’ve got my eyes on a copy Swords And Deviltry as we speak.
I love collecting CDs especially from thrift stores. The hunt for some rare or obscure albums or even some of my favorites is always thrilling.
Recently found the somewhat rare Daron Malakian CD art version of Steal This Album! for $6 and was overjoyed