The most recent sentimental card I got was from the group of friends I play the TCG with. We had been banding together to get chase cards for each others birthdays as surprises and for mine they all chipped in and got me the full art Rosa from Cosmic Eclipse. I have it proudly on display with my Pokemon figures/statues and still feel over the moon when I look at it.
Another would be when I was lucky and got to order a Hidden Fates ETB on their last print run. I wasn’t gonna open it due to how much it was jumping in price but my partner convinced me to as I liked to open packs with her. We took turns opening packs and as we got down to the last few I asked her if she got anything good and she told me to go through the rest of my pack before showing me(I pulled nothing) she then turns her cards around and the shows me the Shiny Vault Charizard GX. I still can’t believe I own it and that she was the one to pull it, I still remember that feeling.