Mine would be creating pen and paper ciphers for my made up secret communication needs.
I was learning Gregg Shorthand at some point just for the fun of it and every time I brought it up people had no idea what I was on about.
I’m old enough to remember when shorthand was a required course for women in secretarial schools. I always though it was black magic and very cool.
In my 60’s. According to Internet sources, shorthand was taught in schools until the 1990’s. It’s likely that shorthand use declined as PCs became common in offices.
I still dabble with orthic shorthand - it’s kind of like seeing language from a different perspective.
I only know about it because of my fountain pen hobby; back in the mid 20th C, Esterbrook made fountain pens with replaceable nibs and offered a wide variety including a Gregg shorthand nib. I guess the Gregg shorthand people licensed the name for marketing. It was basically a normal non, but branded.
Hey! Someone left an old Gregg Shorthand textbook (anniversary edition, if I remember it correctly) in our house back when I was a child, and I tried learning it. Still kinda interested in it up until now.
Tried learning it again back during the lockdown days, but it went nowhere unfortunately.