Charon

Charon, not to be confused with Chiron, is the ferryman that transports dead spirits to the Underworld. He is also the god of boundaries. His mother is Nyx and his father is Tartarus. He resides in DOA Recording Studios.

The Lightning Thief
Percy, Grover and Annabeth asks him to allow them to enter the Underworld and he refuses, but is successfully bribed into letting them board the ferry when Percy gives him two columns of golden Drachma coins (and threatens that if this doesn't work then he'll give more). He asks Percy to tell Hades he wants a pay raise, and when Percy does this;Hades claims Charon keeps asking for more money after discovering Italian suits when they spent some time in Italy where the Roman Empire was.

Appearance
Charon is tall and elegant, fellow with chocolate-colored skin and bleached-blond hair shaved military style. He wears tortoise-shell shades and a silk Italian suit that matched his hair. A black rose was pinned to his lapel under a silver name tag.

Film
In The Lightning Thief, Charon doesn't appear to wear Italian suits, but only a cloak. He also has eyes, while in the book he doesn't. He is simply referred to as "ferry man", instead of Charon.

Trivia

 * Charon, a moon of Pluto, was named after this deity.
 * Pluto is the Roman counterpart of Hades, whom he is serving.
 * Despite him being the god of boundaries, he isn't mentioned to be a god at all in the series.