I can't remember what they were called, but my favourite healing item has to be the ones from Legend of Dragoon (PS1). They are basically the same as the famous "Potions" from Final Fantasy - but with one crucial difference:
Final Fantasy-type potions restore a set amount of HP per use. As your characters level up, their max HP increases, the enemies start doing more damage, and the basic Potion becomes pretty much worthless. So you have to sell off your Potion stockpile and start using the more expensive Hi-Potion. And then THAT becomes obsolete.
Their Legend of Dragoon equivalents handle things differently: The regular Potion restores 50% of the character's CURRENT MAXIMUM HP. No matter how high. A character with a max HP of, say, 12, will gain 6 HP. A character with a max HP of 80 000 will, on consuming the EXACT SAME POTION, gain 40 000 HP. The fancier version restores 75% of max HP.
Can anyone name just ONE other game where a common restorative item aquired on disc one, is still able to save the hero's life during the final boss fight?