Isaac:
Gaia Blade
Warrior's Helm
Dragon Shield
Asura's Armor
Catch Beads
Orb of Force
Grievous Mace
Burning Axe
Vulcan Axe
Bandit's Sword
Mystery Blade
Assassin Blade
Elven Rapier
Arctic Blade
Spirit Armor

Garet:
Wicked Mace
Thunder Crown
Earth Shield
Dragon Scales
Frost Jewel
Douse Drop
Cleric's Ring
Demon Axe
Muramasa
Ninja Hood
Ninja Garb
Kimono
Water Jacket
Elven Shirt
Demon Mail

Ivan:
Kikuichimonji
Lucky Cap
Virtuous Armlet
Storm Gear
Cloak Ball
Halt Gem
Fairy Ring
Glittering Tiara
Adept's Helm
Guardian Armlet
Battle Gloves
Vambrace
Cocktail Dress
China Dress
Spiked Armor

Mia:
Zodiac Wand
Mythril Circlet
Spirit Gloves
Oracle's Robe
Carry Stone
Lifting Gem
Cell Key
Mars Star
Hermes' Water
Shaman Rod / Black Orb
Lure Cap
[anything]
[anything]
[anything]
[anything]

ITEMS FOR THE [ANYTHING] SLOTS:
Unique item (can't be sold; remains in inventory forever):
Dragon's Eye

GS Stat Up items:
Apple (4)
Cookie (4)
Power Bread (4)
Hard Nut (5)
Mint (4)
Lucky Pepper (4)

GS Non-artifact items:
Bone (infinite) (one in GS:TLA as well)
Corn (1) (one in GS:TLA as well)
Fur Coat (1)

GS Tolbi Springs items:
Adept's Helm
Assassin Blade
Battle Gloves
Burning Axe
Cocktail Dress
Earth Shield
Glittering Tiara
Grievous Mace
Guardian Armlet
Kimono
Ninja Hood
Spirit Armor

GS Enemy Drop items:
Kikuichimonji
Zodiac Wand
Spiked Armor

Other Rare Finds:
Crystal Rod (only available after Trial Road)
Demonic Staff (cannot be duplicated at Trial Road)
Magical Cassock (only available after Trial Road)
Silver Blade (only available after Trial Road)