A ninja that uses poisons and toxins to kill his targets. Think a smokebomb full of mustard gas, or poisoning drinks, poison dipped weapons, etc.
Guy1: Hey why are you vomiting blood?
Guy2: Toxic Ninja poisoned my drink, if I die tell my girlfriendI love her.
Guy1: Don't worry, I'll tell her I love her.
Guy2: Wut?