Just as the title said. Which servants in canon do you think are designed the best? By design I mean their servant profile and lore, especially their skills and NP. This is not about their appearance or artwork. Please, I don't want to see more complaints about appearance.
I'll begin. One of my favorite servants is Voyager, and his niche of being an anchor for Human Order, with how his body allows for the perception outside of our solar system. Fits well with Nasu's lore and mechanics.