The answer to everything in the NV.
It allowed Madara to awaken the Rinnegan.
It gave Yamato his powers.
It empowered the Zetsu Army.
It saved Obito's life.
It preserved Obito's deteriorating eyesight from MS use.
It provided both Madara, Obito, and Naruto with replacement arms.
It was used by Kabuto to save Sasuke's life.
It was used to increase the binding strength of the Edo-Tensei.
It was used by Madara and Obito to suppress the Juubi and control the Gedou- Mazou.
It can give someone OP healing.
All hail Hashirama's DNA!!!!