Tetsusaiga. 

Tetsusaiga is the sword used by the Hanyou, InuYasha, in the Anime show, "InuYasha". It was originally forged by Totosai, by orders of his father, out of his Father's fang. It was mean't to Protect InuYasha, but ever since it was broken, it is now up to InuYasha to protect himself, combining the two powers of him, and his father, creating the now Bigger Tetsusaiga, which proves difficult to hold, because of its emence weight.
From what They find, In episode 7, "Tetsusaiga, the Phantom sword" It can only be used by a weilder with Kindess and mercey for humans, coming from his father's love of Inuyasha's mother. Since Shesshomaru has no Mercy for Humans, the sword would no except him.

"Pop left me quite a somthing", Inuyasha.

Tetsusaiga. by Larissa November 20, 2003

Tetsusaiga 

The sword used by Inuyasha in the anime of the same name, it is a sword made by the fang of Inuyasha's father, a full-dog-demon. Originally is a weak, rusted blade, but depending on its wielder's will to protect someone dear, the blade becomes a powerful fang-sword.

Kagome: I've got to take the Tetsusaiga to Inuyasha!

Tetsusaiga by Delf October 13, 2003

Tessaiga 

Tessaiga (“S?Ó‰å, also known as Tetsusaiga) is a fictional sword in the anime and manga series "Inuyasha," wielded by a half-human, half-demon (”¼—d, or hanyou) of the same name. The kanji, directly translated, means "iron-crushing fang."

In the English adaptations of Inuyasha, Tessaiga is written Tetsusaiga (or Tetsaiga) due to an error in translation in the early days of the manga when the tiny ‚Á (tsu) kana (which indicates a glottal stop, or a doubling of the consonant that follows it) was misread as a full-sized ‚Â (tsu) kana, altering the romanization and pronunciation of the word. Both Tetsusaiga and Tessaiga can come from the kanji; the proper spelling depends on how the name is pronounced. The proper romanization, however, is Tessaiga. By the time Viz, the company that translates the anime and manga, had realized the error it was too late.

I'm going to beat you down with (my) Tessaiga!

Tessaiga by Rubyhatchet May 4, 2005

Tetsaiga 

The Tetsiaga is Inuyasha's weapon in the hit anime and manga Inuyasha. It has several abilities: Wind Scar, Red Tetsiaga,Backlash Wave,and Adamant Barrage. it also manages to suppress Inuyasha's demonic blood.

"Inuyasha, use your Tetsaiga!" "WIND SCAR"!

Tetsaiga by James Blalock December 26, 2007