These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Ascended Fanon: Ortega's new sprite/design in the Remix, being born in part of the NES version of 3 over the Famicom's.
Demonic Spiders: The chest monsters. Man-eating chests can kill your party in one or two attacks when you first meet them, Mimics have a One-Hit Kill spell that will try to kill your party members.
Ensemble Darkhorse: The soldiers in general, though the female soldier most distinctly. She appears as various NPCs in future installments of the series.
Fanon/Fan-Preferred Couple: Related, in a sense, to the Memetic Sex God thinking below. In Japan, it is all but a sniff from universally accepted fanon that the Male Hero and the Female Sage are an item and are the couple who start the trilogy's legendary family line. The only quibble in this is what Sage starts off as - there's far less agreement over whether she begins as a Jester, Cleric or Mage.
Game Breaker: Depending on when your Mage or Sage gets it, the Transform spell can qualify as one. Having two or more of your best ally? Yes, please! Not much gear though (until the remix throws in quite a handful. The best is the Rubiss Sword, which has a colossal + 160 attack bonus, casts Thordain for free when used as an item, and everyone can use and equip it with no penalties.)