I'm thinking like Nomad as I like them all, but as far as a favorite goes I think the Silver Eagle is a beautiful coin and the Walking Liberty half that it was based on too.
Achaemenid Empire, Time of Xerxes II to Artaxerxes II, c. 420-375 BCE. Daric (Gold, 16x14mm, 8.37 g), Sardes.
Haven't found one yet, but it's still my favorite type of coin.
Don........