One of my most cherished possessions is something we all have.My life.People I love who is near and dear to me makes this life worthwhile,making them along with the capability of being able to love the most important value of being.I don't think there should be any one particular thing to consider as the most valuable.
I personally think we as humans don't really posses anything physical and our only possession is our soul.
Learn to cherish your surroundings and the people around you and your reward will be richer than any physical item can ever make you.