Programming. I love making small command line programs in python or automating something. Someday I want to make a music desktop app that syncs songs to my phone.
Hot swappable mechanical keyboards. It can be pricey but there's hot swappable keyboards on amazon for cheap, and you can get your own keycaps and switches to create a keyboard that you are really happy with. I love being able to tinker around with my keyboards and swap things out if I don't like them.
Making a "second brain" or personal wiki. I love taking lots of notes (recipes I like, about what I learned, how to fix a software problem, etc) so I can find things easier in the future. I use Obsidian for this, it's really fun.
Lock picking. I got into this for a bit, bought some lock picks and bad padlocks. I watched a lot of LockPickingLawyer's videos and thought it looked fun so I tried it. I was bad at it, it's a lot of feeling when the pins move and stop. It takes a lot of patience but it's really fun.
Making edits to Open Street Map. If you see something wrong, you can go edit it if you make an account and use a map editor.
Raspberry Pi self hosting. I think they are hard to find right now, but it's cool to have a small computer running Raspberry Pi OS (linux) where you can install pretty much anything on it. I run Pi-Hole on mine and it blocks so many ad and tracker domains it's insane.
Making a game. I'm slowly trying to learn blender and unreal engine to make a game. I think it will be fun but also a nightmare.
I think some comment bots are nice, like the TLDR / summarization bot, reminder bot, youtube piped links, maybe one that replaces an amp link with the original? But these bots should be labeled as bots in settings so users have the option to toggle off seeing them.
I don't like having bots post posts though, I've seen some in other instances and there's not much discussion happening in the comments a lot of the time.