At first I read "would not like to see replicated" and I almost got upset, haha.
For me:
- Fountain pens
- Communities for different countries/regions or different language-speakers - on Reddit, I often lurked /r/de, /r/Philippines, etc.
- Mechanical keyboards
- Woodworking
- Oddly satisfying
- Star Trek
- Battlestations
I definitely second BIFL, Antiwork, and different communities for U.S. states, as I don't often get to connect with other people from Texas on the Fediverse.