Laevateinn

The Laevateinn (sometimes Laevatein or Laveateinn) is a reoccurring weapon in the Final Fantasy series. It appears as either a staff, or in some cases, a sword.

Final Fantasy X
Laevatein is a weapon for Yuna on which the dominant ability is SOS Overdrive.

Final Fantasy XI
The Laevatein is the mythic weapon for Black Mage. It increases accuracy, magical accuracy, and magical attack, and enhances Elemental Seal.

Final Fantasy XII: Revenant Wings
The Laveateinn  is one of Vaan's swords.

Dissidia Final Fantasy
The Laevatein is one of Shantotto's weapons.

Etymology
Laevateinn, or "Levatine," is a mythical sword from Norse mythology, also known as the "Wounding Wand" or the "Staff of Destruction". The elf Volund had forged a sword so lethal that it imperiled the very gods themselves. The sword was taken from Volund, brought to Asgard, and passed into the hands of the god Freyr, who traded Laevateinn for the hand of the giantess Gerðr. At Ragnarok, Surtr (the lord of the fire giants) wielded Laevateinn and severed the roots of the world tree Yggdrasil, instigating the destruction of the universe. Freyr would ultimately fall to his own blade during Ragnarok at Surtr's hand.