I have a lot of things which are of enormous sentimental value to me that could never be replaced. I honestly couldn't pick between them... I guess some of my Grandad's old possessions, family photographs, stuff I made as a kid, things from my childhood that I did with friends I no longer keep in touch with, letters that people have written me, my old adventuring stick that I used to hike through the woods with and have pretend sword fights with (that's been in my room for 12 years now!)... man. My Pokemon cards can, literally, go die in a fire if it means keeping any of these things.
I hope people own things that are just as valuable to them. Forgive me and my high horse, but a lot of the stuff being posted here is of purely material worth.