Murasame

One-Cut Killer: Murasame is a sword-type Teigu in the form of a long katana that is used by Night Raid member Akame. Akame Ga Kill!: Zero reveals that it was formerly used by Gozuki, who personally trained Akame and several other children to become assassins for the Empire.

Abilities
Murasame is a poisonous blade that can kill a person with only one cut. Once the sword pierces skin, it injects a lethal poison into the victim, killing them within seconds. Akame states that cleaning this weapon is very dangerous because of this ability.

However, this ability only works on organic things that have a heart, rendering it ineffective against Armor and Biological type Teigu as well as machines.

Lubbock mentions that Akame cannot use her trump card supposedly, so it has never been revealed.