Tinder Polypore: The Firestarter Mushroom
Although its common name describes its fire-starting capabilities, the Tinder Polypore, also known as Horse Hoof Fungus or Fomes Fomentarius, actually has several uses. Otzi the Iceman (link to post) carried chunks of it with him, stored alongside his fire-starting tools, indicating that simplifying fire starting was likely his purpose.