Sentient Weapons

Heroes who are weapons or can turn into living weapons for other heroes to wield. Yukine, Soul Eater Evans, and Susanoo are all perfect examples of this. They are a staple in fictional works ranging from fantasy to sci-fi and even theoretical science. They vary in true sentience as well but must function with self-awareness beyond Artificial Intelligence and/or Golems though they may overlap.

Also, to keep this somewhat separate from A.I.s limit characters to those labeled weapons or with Military connections.