There’s a rare type of blood that’s shared by only 43 people in the entire world. ‘Rhnull’ blood doesn’t contain any of the Rh antigens that 99.9% of humans have. It’s often called ‘golden blood’ because it can be given to anyone who has a rare Rh blood type, but there are only 9 active donors, so it’s only used in extreme circumstances. Source Source 2