Haoshoku Haki

Haoshoku Haki is a rare form of Haki that cannot be attained through training and only one in a million people carry it.    






 



  Shanks is one of
  Haoshoku Haki users






Shanks is capable of using Haoshoku Haki, an ability that only one in a million people can use. After saving Luffy from a Sea King, Shanks was able to frighten it off with a single angry glare using this ability.
Later, while boarding Whitebeard's ship for their meeting, a large amount of Whitebeard's crew (experienced men who have survived in the New World) lapsed into unconsciousness and the ship itself began to take damage from Shanks' mere presence. Whitebeard's men attributed this to his superior Haki.