Robe of the Fire-Rat

While the Fire Rat's origins remain unknown, it is presumed that Inuyasha's father had made cloth from Fire Rat fur, which was used to create a robe. It was revealed in the third movie that Inu no Taishou had it with him before giving it to Izayoi for protection. After her death, the Robe of the Fire Rat was inheirited by Inuyasha. Along with the container of rouge that his mother used, the Robe is the only thing that he has that was her's. Its distinctive red color has become his defining signature look.

Trivia

 * Though the Robe has lost it's power when Inuyasha transforms into a human, it has been shown to still protect Kagome or any other user who happens to be human.