Best 1 drop in the game: May
Best 2 drop in the game: Filene
Best 3 drop in the game: Valse
Best 4 drop in the game: Zirconia
Best 5 drop in the game: Anne and Grea and Aragavy tie
Best 6 drop in the game: Gidaria and Norman tie
Best 7 drop in the game: Kuon (why isn't this 8 like other class board flood bombs?)
Best 8 drop in the game: Cerb
Best 9 drop in the game: Gin and Yuzu
Best 10 drop in the game: they all suck
Rune and Sword are heavily overrepresented on this list as you can see, with Abyss coming up short as 3rd best. Gin and Yuzu is more of a participation award, since there's no other playable 9 drop.