The Resurrection Stone
One of the infamous Deathly Hallows. According to legend, whoever united this very stone with the Elder Wand and the Cloak Of Invisibility would be the master of Death. It has the power to bring back people from the dead, but only as clearly defined spirits who disappear the moment the stone is released. On it's surface is the symbol of the Deathly Hallows; a circle inscribed in a triangle, down the middle of which ran a line, the circle representing the Stone, the triangle representing the Cloak and the line representing the Elder Wand.
Would You Keep It?
After watching this scene I wondered why Harry so easily dropped the stone and did not return for it after the longing he had felt to see his loved ones again. It seems he passed up such an opportunity to have the pleasure of their company whenever he needed it most. However, I then came to understand it would make him the master of death and that, for anyone, isn't a nice title to have. As much as it would be unbelievably wonderful to have the ability to see those who have passed whenever you want to, it's not the way it's supposed to be. It would take me a long time to finally make the decision, but in the end I'd realise it's not the way the world works and taking advantage of something as such is wrong. Perhaps you hold to completely different opinion?