A new material called Proteus cannot be cut using power tools. The design was based on the tough cell structure of grapefruit skins and the fracture resistant abalone shells. According to the linked article, "The material is made from alumina ceramic spheres encased in a cellular aluminum, metallic foam structure. The way it works is like a clever trick you'd see in a superhero movie: It turns back the force of a cutting tool on itself."
I though some of the reader questions regarding using hand tools were interesting and hope to see an answer at some point. I searched the research paper and did not see any reference to diamond tools either.
Anyone want to start a cutting contest?