I seem to collect musical instruments. I'm slightly embarrassed about it so I don't really display them as such but I do have a music room where I practice and we play in there when mates come around.
I play a few different instruments but I seem to have multiples 2 flutes, 2 banjos 3 ukulele, 3 concertinas, 2 fiddles, 4 melodeons, assorted whistles....
And that's not even a complete list.... it's a relatively harmless symptom of my bipolar disorder

My magnets

My teacups

Yes. I have a collection of teacups; were bought in the places I visited and the only rule is that they must be made in England. My second collection is made of about 700 magnets; they represent every item in a household and also were bought in places I visited. I display both collections

On my lazy days, I am known to collect dust. It is really easy to do if you can remain still for long periods of time.

Shot glasses. Only a portion of the collection is on display at any given time.

I used to collect stamps. Well, I say that, but I was actually just given a bag of stamps as a kid and given a suggestion by my mother to start collecting. I never added a single new stamp.

brass bells in the shape of girls , blue china plates with depictions of life and paintings and yes they are proudly diplayed

I have a nice collection of Day of the Dead items, as well as hippos......yeah, two very different things, but I love 'em! I display both but in different areas of my home. DOTD is a bit more personal, so I have those things in my bedroom/master bath. Hippos are in the guest bedroom.

I collect Living Dead dolls, dragonware and rock/crystal skulls. I also have a small collection of gargoyles.

MONEY!!!! Just kidding. Well, I actually do have a decent little collection of coins from various parts of the world, my favorites being an old 2 shilling piece and a modern coin from New Zealand that features an image of a face with traditional indigenous tattoo designs.

I collect shot glasses from places I've been and marvel stuff

Sadly I "collect" most everything, (so far the only thing mentioned by anyone here that I don't have several to hundreds of are the "wooden hand planes" I also have dirt/grass/rocks and water from places I have traveled and those that friends have brought me back when I couldn't go. They are in pretty jars/bottles in my china cabinet. I am not quite hoarder status yet, but my youngest child "the minimalist" is really nagging me.

I used to collect baseball cards until they became worthless. At least the ones I had from the time I grew up are 99% worthless. Cards from the 80s and 90s and sooner are probably worth on average . 1 - . 3 cents a piece. The money is in the cards from before the 60s and 70s really. I think the 50s has the most cards collectively that are expensive. The most expensive card ever is Honus Wagner from 1909 - 1911. It's worth almost $3m now. I used to just enjoy it, but that stopped at some point.

I have a collection of horses, 4 to be exact. They have a pasture and can be viewed up close, or from the road.

Books, lots of books, shell and rocks we find, but mostly books. Shelves of them by author and series.

Both my collections are virtual. I collect Kindle books, and my wildlife/bird photographs. I store photos and videos on Google Drive.