Vinyl records!!! OwO It's not a huge collection, though, since I only started a couple years ago -- not only that, but I've been trying to reign in my spending recently, so I haven't been buying them nearly as often as I used to.
Another thing that I don't currently have a ton of but still consider it a "collection" -- tarot card decks. Specifically themed tarot card decks. I currently have one "normal" tarot deck alongside three fandom-themed decks -- a Homestuck deck, a Night Vale deck, and a Death Note deck. Not only do I like tarot cards in general, I also really like seeing what sorts of images each deck can pair with each card. Sometimes you'll find some clever stuff. For example, the Death card is usually represented as a grim reaper, but I saw one deck that instead pictured a phoenix on that card -- which is actually a lot more faithful to the meaning of the Death card, as it has more to do with ending a certain chapter in your life (and therefore allowing a new one to begin) than it does with literal death, and I thought the phoenix symbolized that quite well. This gets even more interesting with fandom decks, as it's always amusing to see what sort of references they tie to each card. Some of them can be very much a "hah, I see what you did there!" kind of moment. XD And the art in so many of these decks is just beautiful, too. Unfortunately, good tarot decks tend to be on the pricey side, and, like I said, I'm trying to reign in my spending... So I don't exactly spend a ton of time shopping online for these things or otherwise going out of my way to look for them. But I might consider splurging if I happen to see a really nice deck somewhere. owo