Hiraikotsu

Hiraikotsu is Sango's gigantic boomerang and her primary weapon. Like the rest of the arms and armor of the people in her village, it was made from parts of vanquished demons. In Hiraikotsu's case, it was made from purified demon bones. Because of its supernatural material, it's nearly unbreakable and is a very powerful weapon. It appears to stronger than steel, while having the weight of wood. Hiraikotsu's name can be broken down into three components; Hi meaning 'flying', rai meaning 'come', and kotsu meaning 'bone'. The name itself has been interpreted many different ways, but the one that makes the most sense is 'the bone that flies back'  it was destroyed in chapter 485 but was repaired in chapter 488 imbued with a new type of power.

Sango uses Hiraikotsu in many different ways. The leather bands at either end allow her to grasp and handle it easily. At six feet in length and what must be fifty pounds or so (Miroku once said Sango must be strong to carry such a heavy weapon everywhere), she handles Hiraikotsu very nimbly. Other than using it as a boomerang, she can swing it and wield it as a melee weapon. In fact she's killed countless demons like that as well as hitting Miroku over the head when he's needed it. Hiraikotsu is also big enough for Sango to use it as a shield when the need arises, and the nature of its material makes it excellent for that purpose. When not in use, she uses a strap, possibly made of leather, anchored on either end by a buckle and using friction to hold the strap ends in place. She slings the strap over her right shoulder and the strap crosses down her body to below her left hip.

Sango has the basic knowledge and experience to repair Hiraikotsu; she likely was required to learn how to do so, as she sometimes went on exterminations alone. In the anime she had to return to her village to repair a large crack in the surface. The demon bones are worked as if the material was steel. A blacksmith's furnace is used to heat the weapon and bones until red-hot, and more bone is used to fill in the crack, repeatedly struck with a blacksmith's hammer. According to Sango's comments, it was likely her father that taught her how to do so. While she admits that her father's handiwork would have been better, she was able to effect repairs of a quality that she was more than happy with.