I would love the ability for a person to take a patch of empty earth, and symbolically bury a hatchet in it to reflect letting go of a grudge. It would come with a significant mood boost, and perhaps a long-lasting buff that continually provides good mood. After all, letting go of a grudge is therapeutic!
Neat thing about this is that the next person to tend that patch of earth that hasn't buried a hatchet in it gets the buried hatchet as a bonus. So if two people let go of a mutual grudge, bury their hatchets in the same patch of ground, and walk away, and a newbie comes by and tends that patch, he gets two free hatchets to do whatever he wants with.
This isn't meant as a staple game mechanic, but as a neat little social easter egg you can do.