One Piece

One Piece is a long-running anime and manga with spin-offs in other media. So far, all I've actually consumed is the spin-off game One Piece: Pirate Warriors 3. It's a good introduction to the series, presenting a very high-level overview of the major plot events thus far. Since the depth is necessarily lacking, the characters are presented in rather broad strokes. It's very likely that my tiers will change when I watch more of the anime.

Waifu Tier
The best of the best. Only one character may be in this tier for a given work or medium. This character... is Mai Waifu.

Harem Tier
The characters who, while not quite waifu material, rise above the rest.