Natures
Careful raises Sp. Def by 10% and lowers Sp. Atk by 10%. It is applied at the very end of the formula, after IVs and EVs, so the higher the stat, the more the nature gives and takes.
A special wall that hits physically itself: it loses Sp. Atk, which it does not use. A common pick for support with status moves.
Flavor
Likes Bitter, dislikes Dry. This matters for Poffins, Pokéblocks and Berries: a Pokémon eats a disliked flavor reluctantly, and healing works worse.