What is the rarest penny?

Could you please enlighten me on the identity of the rarest penny in existence? I'm particularly intrigued by the question, as I've heard whispers of some exceptionally scarce and valuable coins within the numismatic world. Are we perhaps referring to a particularly elusive variety from a limited mintage, or perhaps a penny that has undergone some exceptional historical event, making it stand out from the rest? I'm eager to learn more about the unique characteristics and the story behind this mysterious and highly sought-after penny.