Here are some potential contenders:
* Hercules (Greek mythology): Known for his incredible strength and completing the Twelve Labors. He's arguably the most famous demigod in Western literature and pop culture.
* Perseus (Greek mythology): Famous for slaying Medusa, a monstrous Gorgon. His story is a classic tale of heroism and bravery.
* Aeneas (Roman mythology): A Trojan hero who survived the Trojan War and founded the city of Rome. His story is important in Roman mythology and forms the foundation of the Aeneid, a famous epic poem.
* Romulus and Remus (Roman mythology): Twin brothers who, according to legend, founded the city of Rome. Their story is a cornerstone of Roman history and identity.
* Arthur Pendragon (Arthurian legend): King of Britain in Arthurian legend, often depicted as a demigod, son of King Uther Pendragon and the Lady Igraine. He is known for his legendary sword, Excalibur, and the Knights of the Round Table.
Ultimately, the "most famous" demigod depends on the individual's familiarity with mythology and pop culture.
It's also worth noting that:
* Different cultures have their own demigods: Egyptian mythology features figures like Horus and Anubis, while Norse mythology has heroes like Sigurd and Heimdall.
* Fame can be subjective: While Hercules is widely recognized, other demigods may have greater cultural significance within their respective mythologies.