Natures
Brave raises Attack by 10% and lowers Speed 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.
For slow heavy hitters that move second anyway — the lower Speed costs nothing, and under Trick Room it actually helps.
Flavor
Likes Spicy, dislikes Sweet. This matters for Poffins, Pokéblocks and Berries: a Pokémon eats a disliked flavor reluctantly, and healing works worse.