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.
Crowning Music of Awesome: YHVH and Satan actually get their own unique battle music, OMEGA, that's so nice many fans of Shin Megami Tensei II are outright disappointed the last several bosses of said game share the same song by comparison.
Many tracks are considered this, thanks in part to a memory mapper that produces higher sound quality than the average NES soundtrack.
Nightmare Fuel: How does losing your arm and having to walk around a post-apocalyptic Tokyo sound to you?
That One Boss: Many. Tiamat, the Hydras, Moloch (who can use Mediarahan up to 9 times!), Lucifer (should you choose to fight him) and Satan.
That One Level: Zaratan Island. You have to explore two opposite ends of the dungeon and you take damage every few steps, PLUS there are random encounters. Hope you have enough MP to keep everyone healthy!
Bael's Castle with its random teleports that send you back outside the dungeon also qualifies.