Here's how it breaks down for me:
When I think of salespeople in the Castlevania universe, the Simon's Quest "faceless gypsies" come to mind as the definitive choice. They're creepy and cool looking with their different colored cloaks. Some of them hide and need to be baited out in graveyards, some seem to taunt/threaten you, and some hide underneath the floorboards of buildings.
Next, I'd probably say Renon, because he was very different, mysterious, and stylish. Plus, the fact that he's really sinister is a freaky touch. (Leave it to CV64 to give you scary atmosphere).
Finally, Renaldo! I liked how his story had some depth and was intertwined with the hero's. His voice actor was excellent and he was actually interesting to visit with all his stories/advice.
Runner-up: Librarian of SotN. He almost made my picks because of his personality, but he came up short.