Mine is a double answer, but they're kind of a combo so it should count.
My signed Mamamoo album and poster from their Pink Funky era (2015)
I don't value them more than anything simply because they're signed. Oh no, I value them because I watched each member of Mamamoo sign them in front of me, when I attended the first ever U.S. MooMoo fan meeting back in 2015.
They were never again as accessible as they were that day, just a few months before becoming one of the top girl groups in Korea.
The signed merch is awesome, but it's the memories and what they represent for me that make them cherished. After I booked a flight to LA to see Mamamoo, I've flown all over the country, and even to Asia, to see them and other groups.
But you never forget the first time you meet your favorite idols in person. Especially when you literally get to spend minutes chatting with them.
Maybe one day I'll post the pictures I took with them in Tokyo (my second most prized possession), if I ever feel like revealing my powerful visual status
Okay, someone else go.