Oh boy, you are asking the wrong person because I am a collector by nature. My favorites are gemstones and books (mainly art and mythology.) I do collect art itself and have many portfolios filled with them as well as framed pieces.
Some of the other things I collect are cassettes because they are some of my favorite media. Although I also collect video games. It hurts my heart how little the video game industry protects their IPs and how many video game have been simply lost to time.
My last three collections that I don’t typically talk about are my magnets, keychains, and stickers. I purchase magnets from various locations I visit, such as zoos, aquariums, and rescue facilities. I also collect keychains that represent different regions I have been to, particularly states, although I have a fondness for keychains in general. Stickers are among my favorite. I refuse to use them, however. Instead, they have their own portfolio to sit in since most of them are actually art pieces.