I’m quite fond of the aurochs. As the feared onager was to the domestic donkey, so the aurochs to domestic cattle. Onagers gave their name to a medieval siege weapon; aurochs gave their name to a letter of the runic alphabet.
Both onagers and aurochs are extinct now, although some breeders have been attempting to bring back Bos primigenius in the form of Heck cattle… the cattle from Heck!!!
Illustration from Webster’s New International Dictionary of the English Language, 1911, G & C Miriam Co. Springfield, MA, [found here.]