I often have these urge to collect things I couldn't collect back when I was a kid (lack of interest, money and these things are very hard to find where I live unless I go to either another country or the main capital of my country which involves taking flights or ordering online).
Raw japanese mangas and magazines (the english officials are often expensive and have not very satisfying if not inaccurate translations)
-These are very precious to me since I didn't have the ability to order things online back then, so I had to buy them in person (I had to travel via plane to get them). I get very defensive and agitated when someone mistreats them, even as to so much warn them not to bend the books in particular ways. To put the cherry on top, I cover them in plastic.
Stationery
-I guess it's an artist trait to blow off a lot of money on utensils where you don't even use 3/4 of them. I have collected art pens where some I'm reluctant to use (cause they're expensive and sold in very limited places), tapes, papers, sketchbooks, etc. There are empty pens and containers that I don't bother throwing out (unless I have to) cause I often see use in those junk (like fixing a slanted table).