I would love it if when my pet animals (and all animals in general) died of old age that they'd leave behind a parting note. Especially if it was signed by them. So when my piggie named "Zebra" dies, I could get a note of farewell signed by Zebra... so I could make Zebra Jr. or Zebra Porcine the Third.
And it has fun possibilities for interesting notes. Ones reflecting on life, grief, even the pain of living. Or humorous or deep and hinting of transcendence into a different imagination. In sensitivity, it wouldn't be appropriate to leave behind "suicide notes", because of the issue in real life, but it could be a doorway into conversation, and I would think that the one in 10,000 note that way might be profound. Heck, I could imagine collecting the various notes even if they had no monetary value. (I hope they wouldn't have a currant value, but could be auctioned.)
It'd also be cool to note where various animals in the streets had died as some notes would be left behind by players.
Or, possibly little tombstones, though I prefer the notes.