I uploaded the most recent version of my "Item Compendium" document. Same URL as before:
Looks good... I'll have to dissect the spell power of the items at some point to see if any of that even makes sense to me.
I've kinda concluded that item magic has a hit rate of 100%, overriding whatever spell hit rate data it is basing itself on.
Some descriptions of the weapons:
Lightbringer: How to get this and the Caliburn is documented in the FF4A Lunar Ruins guide for Cecil's trial. It's the weapon given to you if you successfully passed all the tests.
Caliburn: It's a play-on-word thing that should be obvious that failure was achieved.
Avenger Sword: Being under Berserk status increases your damage output by 50%... and perhaps one of the better weapons for Kain for FF4.
Slumber Sword: Sleep can be cast by the weapon. The spell's effectiveness under this weapon is primarily driven by level.
Blood Sword/Spear: It is very effective against flan/pudding monsters and Giants. The only monster worth worrying about is the undead and particular FF4A's undead flan monster (I forget its name off the top of my head, but that monster can be found on the "flan" level and in the FF4A beastiary...)
The "Piglet Sword" is aka Piggy's Stick in FF4A. The one found in FF4ET is found in the pot in the pathway between you and Odin at Baron. The one in FF4A is found in the "Chocobo Forest" in the Lunar Ruins. Both have a chance to inflict piggy status on attack.
Abel's Lance: It's Kain's "ultimate weapon" in FF4A. It's simply overpowered. Lightning elemental.. and one of the few spears (like the Blood Spear) that does NOT have the Aerial attribute (I feel that's a bug, but I digress...). It has a random chance of casting Tornado.. which relies on Kain and the target's level. This version of Tornado ignores the boss bit, making it grossly overpowered. This is picked up after the successful completion of Kain's trial.
Blood Spear/Lance: One of the treasures dropped by one of the monster-laden treasures in Eblana Castle. This weapon IMO is weaker than the Blood Sword (not by much) because of its atrocious hit rate.
Hand Axe: Probably was meant to be available when you got Cid, so figure. It is never normally available in all versions up to FF4A (FF4DS is unknown AFAIK).
Rune Axe: It is dropped by those Giant-mechanical-like monsters. You have the best chance of acquiring one during the Giant when the Searcher monster summons a MacGiant. This weapon is the anti-mage killer. It is unfortunately 2 handed.
Mute Knife: It's not really that great with Rydia. It is relatively beneficial for Edge most of all, because he wields two weapons and has the strength to kill mage enemies at a whim.
Lilith Rod: It has a greater spell multiplier than Tellah's starting Wisdom, so it's actually a significant improvement, plus you don't have to wait for the Pysch/Osmose spell to be cast.
One other thing, there should be a byte designated specifically for certain items (Ether1, Ether2, Elixir) that makes them sell for 1 GP... they don't have a 1/2 sale price.
Byte 0 for the weapons extra attribute (as far as I'm concerned) is the "prevent critical hit byte". If you've ever noticed while using those weapons, critical hits never occur. I forget if Dragonsbrethren confirmed that. Byte 5 for the weapons enemy bonus is for flan/pudding monsters.
Also, the spell based items.. the ? is the spell hit rate... with the highest bit (bit 7) is the "boss bit" (when set, it doesn't work vs bosses). This bit also applies to the spell hit rate list.