Anduril

Andúril, also called the Flame of the West, is the reforged sword from the shards of Narsil.
It was the sword of Aragorn II Elessar, heir of Isildur.
The shards of Narsil appear as Bilbo Baggins explores Rivendell, after he, Gandalf, and Thorin Oakenshield's company of dwarves take refuge in the town during their quest to reclaim Erebor. Bilbo passes by the shards of Narsil and the altar they were laid upon, and takes a brief moment to examine the fresco that showed Isildur raising the hilt of the broken sword against Sauron, of which Bilbo's attention is drawn towards the One Ring on Sauron's hand.
The sword's first appearance, as Narsil, is in the possession of Elendil during the Battle of Dagorlad, holding it high to rally his men to him. Sauron emerges and kills both Gil-galad and Elendil. Isildur rushes to Elendil's aid, but Elendil is already dead. Isildur picks up the sword to fight Sauron himself, but Sauron knocks aside Isildur's attacks and stomps on the blade, shattering it into several pieces. Sensing victory, Sauron reaches for Isildur to finish him off, but the Man, unbowed, manages to use the hilt of Narsil and what remained of its broken blade to cut the One Ring from Sauron's hand. It is not seen again until Aragorn and the hobbits arrive at Rivendell under the guard and care of Elrond and his Elves.
After Aragorn and the Hobbits safely arrive in Rivendell, Aragorn takes time to rest and is reading Elven literature when he is disturbed by Boromir's intrusion. Boromir, seemingly in awe of the mythical sword grabs the hilt, runs his finger along the blade and cuts himself — surprised that the blade is still sharp after 3,000 years, then accidentally drops the hilt on the ground when he catches Aragorn staring at him. Aragorn, out of respect, picks the hilt up and returns it to its rightful spot.
The sword is not seen again until The Return of the King when Aragorn and the Rohirrim were camped at Dunharrow. Arwen pleaded with her father Elrond to reforge the sword, convinced that the enemy could be defeated. Reluctantly, Elrond agreed and had the shards of Narsil reforged into Andúril by the smithies of Rivendell. The sword was then engraved with runes saying "Anar. Nányë Andúril I né Narsil i macil Elendilo. Lercuvantan i móli Mordórëo. Isil." in Quenya, which translates as "Sun. I am Andúril who was once Narsil, sword of Elendil. The slaves of Mordor shall flee from me. Moon".
The sword was presented to Aragorn at Dunharrow by Elrond, who, along with Andúril, brought grave news. Elrond's daughter, Arwen, was dying. His other news was equally grim: a fleet of Corsairs were sailing for Gondor. Elrond had one piece of advice to temper the ill news; If Aragorn took the Paths of the Dead, with the power of Andúril (formerly known as Narsil), he would be able to call forth an army greater than any living army, and with that army he would have a chance to stop the Corsairs and save Arwen. It was this sword that manages to have effect on the leader of the residents of the Paths of the Dead, unlike Legolas's arrow or Gimli's axe. 
Just before the battle before the Morannon, Aragorn confronts Sauron through Denethor II's Palantír, and goads him by showing him "the sword of Elendil" that defeated Sauron during the Second Age.