These are items for specific stages. Info on these can be obtained in the walkthrough

Arms (sword/shield/armor)

Blade: Its power goes up as you acquire the four guardians. It starts at 4, then gues up to 8, then 10, and finally 16

Mail: Your starting armor

High Armor: Simply reduces damage taken. Get this in the beginning of stage 4. Look for a bridge that has a bunch of conveyor belts on it. On the other side is the room containing the High Armor.

Guardian Mail: Reduces damage even more than the high armor. Get it by collecting the 4 metals in stage 7.

Shield: Does what any other shield would do. Protects you from certain projectiles.

Guardian Shield: Pretty much the same as above.

Hold Items

Holy Water: Restores vitality when it runs out

Magic Stone: Restores SP and MP when both are depleted.

Izanau (I think that means "Come here now") Bell: You don't get this until stage 7. Lets you lets you pick one of the five partners and switch between them at any time.

Guardian Blades

(See the Guardians section)

Dropped/Treasure Chest Items

Aura Blade: Makes your sword shoot energy.

Elixir: Completely restores vitality and MP

Energy Drink: Restores some vitality.

? God Orb (can't read the first kanji): Increases max MP

L-Potion: Restores MP

Life Orb: Increases max vitality

Potion: Restores some MP

Telesma: Restores SP