There was this one point in time where I thought having two FireClaws was better than one.

Anyways..
If you bothered with Eblan Castle..
Slumber Sword - It's certainly worth the gamble, since it is a gap weapon between the Fire Sword and Silver Sword. Since Sleep is primarily level based, it's success is tough to gage sometimes.. although FF4A made it pretty overpowered by design (making Sleep work 100% of the time).
Mute Arrows - You'll buy them later, but for only a small set, it's primarily non-impactful.. although it's best day is if you use it vs the Magus Sisters. It's amazing how a 4x attack power modifer shreds stuff quickly.
Drain/Blood Spear - There was a point that I used this exclusively, but stopped when I wanted reliability. I guess it's the answer for the Flans/Pudding you meet at the Tower of Bab-il (underground), but meh. Although, this is my favorite weapon vs the Mad Ogres... especially when it comes to monster harvesting. There's a lot to be said when it comes to "free healing"... though the Ogre Axe and its complement, the Blood Sword is actually more reliable.. which make shock some people.
A Lot of Trash Later and the Invisible Tower of Zot
Prisoner's Robe - I forgot about this, but the Sleep property may be worth it, but it's more or less like a Cloth that actually has some value. It's nice that you get a pair, (Is Rosa sexier in stripes? Cid probably says no.)
Charm Claw - It's got to be the most awesome, overpowered, and yet perhaps balanced weapon for Yang. The hit rate is the equivalent of fist, but Charm status is worth the bonus, even if your overall damage is lowered as a result.. you can trash Ogres and other Giants like candy. Plus, it boosts Agility, which cannot be said for
any weapon up to this point in the game.
Strength Ring/Power Wrist - A common drop by Ogres is actually worth over the crappy Mythril/Silver Gloves. You're not giving up much... too bad it's still metallic.
Zeus/Giant's Gloves - Even better than the above option, and isn't metallic.. it's actually pretty damn good for gloves, until late game. The lack of magic defense is not a big deal, considering the alternatives, plus feeling overpowered is good. However, this is a rare drop and is "much easier" to obtain in the Tower of Bab-il via Cave Eblana...
Fire Armor - It is put in the most interesting spot, if only to allow you to rape yourself when you fight the FlameDog for the Fire Sword. Amusing nonetheless.
Fire Sword - Burrrrnn. Its best attribute arguably can be its worst attribute later on. Go figure.
Flame Shield - This is handy if you want to use this later for elemental protection... it's best in shield form IMO.
Poison Claw - The status effect is useless, which is the same as my opinion on Poison Arrows, which I forgot to mention earlier, but it's worth pointing out here... the major benefit is increasing the hit rate, if not allow balancing out with the Charm Claw, which has a weak hit rate. Strength boost is more of a "meh" bonus.
Poison Arrows - Dropped by the entire set of Hydra enemies (and a few Naga varients)... it's stronger for when you have it, but Poison is the most non-impactful status on a weapon that there ever was, unless used against you...
Earth Hammer - Making it Fire elemental is perfect for what you need it for.. plus a free Quake spell is insta-Flan killer (it's better than other alternatives, which includes Yang using is Build Up/Power command).
Wizard Robe - This is the only time that Tellah looks actually competant with his Cure3/Curaga (well, particularly if it is single targeted)... too bad he still sucks.
Rune Ring - If you fight a lot of those Marion guys, you may get a few of these. The longevity of this ring can extend to the Lunar Subterraine as the Diamond Ring is not really impressive. Silence protection plus some stat boost may even make Tellah look like a genius.. for two seconds. Plus, the Mage protection would be a bonus if you do a lot of monster harvesting to boot.
Silence Staff - This is one of the few weapons worth looking to acquire, given that relative to Rosa's other weapons for a time period, this is actually a good weapon (well, you will auto-abuse the back row bit right?) Plus, Silence is a handy spell (although it's cheap to cast) plus it will be better than any staff you could buy, up to a point. This is worthy of a look. At least you are given many chances of acquiring this....
Wind Spear - I wonder why it can't be thrown (I mean who's dumb idea is this?)... it's only close to the Slumber Sword, but not by much.
The Dwarves and Their Freaky Eyes
Flame Spear - Free Fire2 makes killing Dark Imps a breeze. It's not that handy overall, but I like free stuff...
Dwarf Axe - I often wonder why this doesn't have the Air elemental, especially given the weapon itself. Oh well, at least there's a nice axe throwing animation (via the Throw command) that normally gets seen in FF4ET... This weapon is underrated, but annoying at the same time. I don't like the Agility loss in addition to the Wisdom/Will/Intellgence/Spirit loss... but oh well. These are better weapons vs those FlameDogs, and particular the damned Chimera.
Darkness Arrows - As I said before, they are underrated primarily because Ice Arrows tend to be more effective at killing many of the underground's vile. This is one of the few status afficting weapons that are worth it if you want a monster's counter or spell to become far weaker... if they aren't resistant.
Wizard Hat - Undead resistance is a nice bonus.. anyone who doesn't recognize the massive undead usage is crazy. Plus, Cecil can equip this.. which is an improvement over all the previous options.
Medusa Arrows - Very powerful stuff, if you are overleveled...
Black Belt - It's an improvement over the Karate Robe (I didn't realize it until many years later) but can be used to improve Rosa's offense, though sacraficing Will Power/Spirit bonuses... though Kain+Cecil can definately benefit...
I forgot to mention...
Charm Harp - This harp is better for Edward obviously.. but for the Battle @ Fabul.. it is useless vs the General.. since he'll make his soldiers attack. The Dreamer Harp is still better for stopping the General...
Back to everything else...
CatClaw - You could probably get it early via lucky drops.. but it's a pretty damn good option for putting most monsters to Sleep.. since Yang tends to gain levels quickly, he will make short work of monsters anyways.
IceBrand - Better than the Fire Sword, but the Fire Sword may have a few uses before you really want to sell it.. elemental blades vs Chimera = poop.
Blizzard Spear - Ice2 is a nice Tofu killer.. especially in the few formations they appear in. Still sucky vs Chimera.
Ice Shield - The best attribute is protection against Reptiles.. but an even better idea is to use them in conjunction with the Fire Armor for great elemental protection (except if Cecil or Kain hit themselves, which actually can be very devastating).
Ice Armor - The shield is better.. but it's best to pair with the Fire Shield. You know, those Chimera and FlameDogs don't look so tough then (except everyone that is not named Kain or Cecil will be torched).
Bandanna - It's an improvement over the Headband, but I'd still keep the Headband for later...
Archer Bow - Another Meh.. even though the boost is nice.
After The Cannon Goes Kaboom!...
Black Robe - The weirdest armor ever when it isn't the original FF4... go figure. Ultimately I believe this was supposed to help Rydia survive Rubicante.. but eh.. it's not that helpful.
Boomerang - This weapon is perhaps worth a look. There's a number of enemies that can be exposed by it, despite it being weaker overall, but can easily expose the Back Row bug for Edge... probably one of the few underrated weapons.
Power Staff - If they kept the Berserk spell of this staff, it would've been more useful. There are very impactful consequences when Berserking enemies on hit, even though this allows Rosa to be a better fighter.. with a staff... it may not be worth that hassle. Berserk tends to be a benefical status, and people who don't realize that need to rethink the number of times they use the Fight/Attack command...
Middle Katana - If it's actual impact is to allow the Short Katana to be thrown away, that's about it.. I don't get why more of his Katana can't be thrown away. I can understand the elemental swords, but not this? Go figure.
More to come later... in a separate post starting @ Tomra.