I've always liked how different JRPG series have their own subset of items, currency, and other staples of the genre. Most games feature the same selection of healing/recovery items from a functional standpoint, but they are just themed differently to fit within each game's respective vibe/world. Whether it be potions, herbs, Phoenix Downs or what have you, I'm curious to know what everyone's favorites are.
I'll throw in my vote for Gels in the Tales series.
An apple gel.
I'm not even the biggest fan of the Tales series, but I've always liked their charming use of gels with varying colors and flavors that all serve different purposes. I just find the idea of consuming little gumdrop-esque candies to heal yourself to be very cheeky and Japanese in that typical JRPG way. What's funny is that the implementation of these items is kind of lazy compared to other RPG's, since they are all just palette swaps of the same pixel art.
PS - Anyone who is into the idea of running an item shop in a JRPG town needs to check out Recettear if you haven't already.