I agree, they're maybe more like standard items. That'd put them in the same category as collecting the bonus items in LoZ or ALTTP
I'll go with mine: Actually it's gratitude crystals! I liked how they are all tied to specific quest lines, and I liked Batreaux a lot, and the whole intersecting...
Every, or almost every, Zelda game has one major collectible outside of Pieces of Heart.
I can't name every single one from the top of my head, but here's what comes to mind:
Gold Skulltulas (Ocarina)
Masks (Majora's Mask)
Treasure Charts (TWW)
Secret Seashells (LA)
Rings (Oos/Ooa)
Poe Souls...