Shanks

Little is known about what Shanks can do, as he has not been seen heavily engaged in battle yet although as a member of the Yonkou in the second half of the Grand Line, his power is considered equal to that of Whitebeard and "losing an arm did not weaken him in any way".

Shanks is usually portrayed as a swordman. Ten years ago Shanks was capable of swimming, meaning that he did not consume any Devil Fruit at the time he was a rival to Mihawk. 

He appears to be an excellent swimmer as well, having reached the young Luffy in time out in the middle of the sea before the Sea King could devour him.

Shanks is also powerful enough to stop Akainu's magma fist with his sword and Busoshoku Haki.

According to Buggy as a young man, he was a strong fighter and had it not been for his ideals, he (Buggy) would have wanted him on his crew.

As a member of the Yonkou, Shanks' name alone can command great power, as Buggy himself proved; his assertion that he previously had a "brotherly bond" with Shanks was one of the many things that earned him respect from the Impel Down inmates. In addition, Buggy did not shy from using Shanks' and his previous Captain's name Gol D. Roger to maintain his respect amongst them. Even the fact Buggy was seen backtalking to Shanks was seen as a testiment of Buggy's own power, not aware that the two had always acted like this and mistaking as it was because Buggy wasn't afraid of a Yonkou.

Shanks commands enough power to end the war at Marineford with just words; when he stated there was to be no more fighting, no one stepped up to challenge him even though the marines were fired up after the death of Ace and Whitebeard. When he offered to fight the very overconfident and pompous Blackbeard Teach, (who moments before boasted about destroying the island and taking down Fleet Admiral Sengoku and Vice Admiral Garp) he declined and decided to leave as it was too soon for them to take Shanks on. This is most interesting because Teach had rushed to finish off Whitebeard (although it should be noted that Whitebeard was already heavily wounded), who was considered the most powerful man in the world and a monster unlike no other, yet declined to fight Shanks. Furthermore, when he requested that Whitebeard's and Portgas D. Ace's dignity at death not to be violated, Sengoku himself decided to call off the war, and offered to take responsibility, showing that despite being a pirate, he has earned Sengoku’s respect, something that no other pirate achieved other than Whitebeard.

Shanks is one the very few characters who can use all three kinds of Haki. 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, half of Whitebeard's crew (one must note those are 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.When Shanks and Whitebeard clashed with their weapons, the "heavens" above them split, hinting the incredible Busōshoku Haki that the Yonkou had imbued in them.

During the Battle of Marineford, Shanks was also capable of stopping Akainu's magma fist, imbuing Busoshoku Haki in his sword.