Unsurprisingly (this is literally an Animal Crossing forum lol) I collect Animal Crossing junk.
Stuff i have now:
ACGC, ACCF, ACNL, ACNH, Isabelle and Digby amiibo figures, Tom nook island getaway plushie, kappn and porter plushies, island getaway t-shirt, Japanese ACNH Tom nook t-shirt
I also collect Coca-Cola bottles, particularly those Mexican glass ones (infinitely better than the American ones btw). I also have a few other soda glass bottles
I collect plushies: I have a lot of San-x plushies (I think that's the brand)
I used to have a collection of 20 pebbles when I was younger, because I loved the novel
Stargirl. (The titular character also had a collection of 20 pebbles which she used to describe her mood.) Once when I went to church camp, I brought home a big rock in my suitcase just because I could.
I collect stationery, mainly ~aesthetic~ pens and highlighters. I have so many! Pack of 100 Gel pens, Zebra highlighters. Double tipped metal/felt pens. Papermate... clicky ballpoint pens...
Also various mementos from the trips I've been on - Disney world, Hawaii. Sorta fake Playbills from unofficial plays from several years ago.
And cards. Don't forget cards... I had family members who, when I was younger, sent me cards for every occasion. Mainly my grandma and great aunt. Birthday cards, Valentine's Day cards, Easter cards, invitations.... I will also admit that I have a whole stack of pre natal cards my mom received when she was pregnant with me! (Baby showers, well wishes cards, even lists she wrote of things she would do with me when I was born
)
Wow I did not realize how much I collected until now lol.