Hood ornaments tend to be pretty boring these days, mostly because there aren't too many brands out there, and there's not much room for personalization—even Rolls-Royce sticks to its famous "Spirit of Ecstasy."
Go back 100 years, and folks ordering up custom-made cars could slap pretty much anything they wanted on the hood. But that doesn't answer why William Wallace Jr. had his 1911 Fiat Tipo 6 (being auctioned off at Pebble Beach this weekend) come topped with a Native American riding a snail. That said, the snake head for the horn is sweet.
Anyone with an answer on the snail thing should let us know: @Autopia.