Well, some of them have a good reason for being rare.

Fang of Vog - It's expensive, hard to get, and lights you (and allies) on fire when you use it. The Combuster/Shock Edge are safer, seems to have a slightly more useful charge, and have great synergy with Hail Drivers. The DA is also popular, but that's more because it is overhyped than anything else.

Winmillion - I don't think it has a 5*, does it?

Iron Slug - If you want a normal gun, the Supernova and Valiance deal better DPS, are easier to use, and safer.

Neutralizer - Again, it just pales compared to the Supernova and Valiance. The biohazard line has shadow and poison going for it, the Neutralizer has nothing.

Sentenza - This gun is almost impossible to use against it's intended targets (beasts and gremlins) due to the nature of their dodge, and like the AP it suffers heavily from being a dual-damage weapon. Outside of PvP (where it shines thanks to using elements most players have no resistance too) it's pretty meh bordering on worthless.

Supernova - It's a good gun, but most people prefer making a Polaris instead. Still, I would chalk up the lack of these to the generally low concentration of gunslingers and the token requirement.

Callahan - Most gunslingers either discover the Blitz Needle (which is much, MUCH better.) or end up swapping this for a Polaris/Driver/Peacemaker when they start in FSC. Quite frankly, this gun is given too much credit by many gunslingrs. In my own opinion, it's not that good of a gun. Against Fiends (Trojans and Greivers especially, but groups of devilites too) the Blitz is just outright better. Against wolvers you are better off using a sword or (preferred) a bomb.

I personally use my Blitz for fiends, and a Dark Briar Bomb for killing groups of wolvers.

Big Angry Bomb - The Radius, fuse, and knockback make this an inferior bomb. Especially since I hear it's damage isn't much better than the nitronome.

Irontech Destroyer - Doesn't this only go to 4*? Either way, the boost aganist constructs really isn't worth giving up overall damage. Most bombers are either better nitro chaining or haze-kiting.

Venom Veiler - The poison doesn't last long enough to make it a worthwhile bomb.

Stagger Storm - well first off, to get this you need what? 300 Tokens? And you can't buy the recipe on the AH, you need to farm them yourself.

Secondly, the stun status effect makes many monsters behave unusually. Zombies will sort of slide instead of jump, and not all attacks are stunned. Plus any attack in mid-swing when the stun wears off will go to completion at normal speed. Making it a dangerous bomb to use.

Ionized Salt Bomb - Damage Bonus VS Slimes on a Pierce weapon. 'nuff said.

Take it from me. You'll have lots of fun with your Polaris down to FSC. Trust me. I own it too.

I use a couple of your rarely seen weapons, so here are my thoughts. Keep in mind that I'm primarily a bomber, so my non-bomb weapon choices are mainly to complement that.

Sentenza: I use this for gremlin levels. The gun is faster than gremlins' ability to dodge it, in fact they mainly just back up in a straight line, interrupting their attacks. You can basically hose them with shadow bullets and kill them off quickly if you're not a spazz when it comes to aiming. Note that I prefer this over the Graviton Vortex--I hate the lower movement speed with that thing. Also, while I haven't used it for this yet, I've read others saying that it's still useful for Vanaduke fights--Vana isn't undead, so you don't get the bonus from the AP, and they end up doing equal damage to him.

Venom Veiler: People think poison sucks, but it's still useful. Since I have bomber gear, plus CRT UVs on most of my bombs, I have Maximum CRT for most things. I can lay a lot of the hazes very quickly. The VV is wildly useful when you're in an arena when menders/silkwings. As long as either you or someone in your party can handle the direct damage of taking out the enemies, then the VV can be used to keep them from being healed. This goes for His Jellyness as well. During group JK fights, I mainly just lay down a field of VVs so that he never gets a chance to heal. I tend to carry both that and Ash of Agni into the palace, along with a sword.

Ionized Salt Bomb: Sure, it's not an ideal weapon, but I actually used this quite a bit when I was a Baby Bomber. It's not perfect for anything, really, but it has an all-around, if low-level use. There were times I'd take out arena mobs on my own just using one, often times carrying the rest of my party through to the end of the room. Even mech arenas, they don't take much from the piercing, but they do take some from the elemental and shock. I've since replaced it with, well, nearly everything else, but it was still a decent weapon at the start.

Fang of Vog: OK, I don't have this, but even those that do I've rarely seen use it, for the reasons mentioned above. I have a Combuster and that's much safer to use when I want to set things on fire with a sword.

The rest of the criticisms I tend to agree with.

I actually crafted Callahan aka dirty harry because of the good reception it was getting from gunslingers. I have to say its a great gun for fiends due to it being a ranged weapon. It essentially replaces the barbarous thorn blade for us sword users. Still, I prefer barbarous thorn blade to fight wolvers and greavers. When it comes to devilites, I'm definitely bringing the callahan. (Does 260 dmg/per shot versus Vanaduke!)

For neutralizer, I kind of regret crafting one. Its too impractical to make any use of it. The only monsters I ever use it on are the Lumbers and Lichen Jellies... and that is if I even have time to put charges on them. I might have to sell mines so I'll just end it here.

The weapon I see less in general are the guns. That said with other weapons and bombs, I do have some of the weapons in your list. Simply because I'm not really playing the game to reach Vanaduke, but because I followed the alchemy path just cause. Mostly a sword user I have the Wild Hunting Blade, the Barbarous Thorn blade, the Winmillion and the most recently Triglav (Currently Jalovec).

I'm a full Wild Hunting Blade user though. I picked the weapon for kicks and come on, it's a wolver "at your side". (Not to mention a bark bite from it could be a whimper sometimes when you attack). Maybe if 3 rings happen to release more tier 2 or 3 bosses in the future, not many people will depend on the same weapons. It is yet a small scale game though, who knows.

Callahan is great but it's really for pure gunners. If you'd prefer to use a sword or bomb, go ahead and you're probably better off for it. But if you're purely using guns then Callahan is your friend against Wolvers and Devilites.

In terms of those bombs, Irontech and Big Angry Bomb sacrifice too much compared to the Nitronome for their slightly higher damage. I'm pretty sure they both slow your run speed while charging too, which is bad while kiting. Ionized Salt Bomb takes about twice as long to charge as Rock Salt Bomb. Also it is a Piercing weapon designed against Slimes. Radiant Sun Shards deals Elemental/Piercing damage so it can be used with some success against just about anything, and charges at the same speed as the rest of the Crystal Bomb line.

I have a Flamberge (from before I went gunslinger), but if you compare the damage of the Final Flourish to the Furious Flamberge there is quite a difference. Also, the third strike of its charge attack (for my 3* version at least) can set teammates on fire. :3

The Fang of Vog is a monster of a weapon, if you can handle it. I bring it every time I run FSC. It's brutal on trojans doing 400+ damage (tier 3) with each hit of its charge attack. Charge does 500+ on undead! What weapon is comparable to that for FSC? I would love to get a CTR vh on one of these babies. Of course if you're not properly equipped to deal with the flames then this is probably not a weapon for you...

Yes, the AP is useless everywhere except for vanaduke. Hence making Sentenza better :)

I tell you why...

I agree with Notbob. Gremlins and wolvers dodge alot, but you want them to rather dodge you or hit you? The gun shoots fast, so it's easy to hit them, even if they dodge. In arenas and tight spots, you basically have them on lock because they have no where to go.

Also, the best guns in this game are elemental ones. Hence, why you would want a shadow/piercing gun. The other shadow guns are decent, but you want speed for your gremlins right? So the only other option is Umbra driver. As for piercing guns, all them have reduce mobility, which is not what you want when you fight wolvers and fiends. As a gunner, the blitz and callahan just does the job too slow and only makes you vulnerable to attacks.

Therefore, Sentenza = pwnage

I can't say anything about most of those weapons but..

Wild Hunting Blade - This was my first piece of 5 star equipment ever and I was greatly disappointed. The slashes from the sword cause the enemy to be knocked back too far for the wolver to bite down into them (unless its a huge enemy or if you knock them into a corner) so you're doing a very low amount of damage overall. The sword is also outshined by weapons that do piercing style damage which can demolish wolvers AND fiends.

Callahan - I got this gun not too long ago. I can definitely say that its getting the credit it deserves. Its also a VERY very fun gun to use. It feels good to annihilate wolvers and fiends with a gun in a few shots. Yes, a piercing sword would do better against wolvers and fiends BUT this gun is also very helpful against Vanaduke's last stages. Sorry Jamini, but when it comes to piercing guns I'll stick with the Callahan over the Blitz Needle.

Sentenza is just so silly to use against T3 wolvers though, it'll just make them teleport everywhere and bite you in the rump! Specially hellish for any swordies since they would not get more then a single hit if your just shooting it off. I have a mega magnus and as much as I like it I think I might just go with DBB for fast destruction.

Honestly I'll probably be getting a Winmillion for kicks and the occasional JK runs, because come on a sword that ALSO throws projectiles on normal attack? That's just badass.

I am a dedicated Supernova user. I swear by it, and love it to bits.

The reason I prefer it over Polaris (which I also use, on an alt) is because I solo a lot. Its normal damage lets it fit alongside a single sword (the single best all-purpose sword out there, Leviathan, of course) and retain perfect coverage without needing a 3rd weapon slot. It's a lot like Valiance in that regard; a solid, reliable sidearm, but no good for a full-on gunslinger. But unlike Valiance, its consistent knockback and flinching allows you to control groups of monsters. You can push back hordes, and corner and execute lone tough mobs like Lumbers. And it murders gun puppies just as reliably, if not as quickly, as Polaris.

The major downside to Supernova (and Polaris) is the annoyance you get from teammates, particularly swordies who are blinded by the flashes, or whiff on their charged attacks when Supernova's knockback hits first.

EDIT: After giving it some thought, there's really only one thing Supernova can do that Polaris can't: take out gremlins. Against everything else you'd use a gun on in T3, Polaris is deals neutral or better damage, and has a shock chance besides. However, soloing a crowd of gremlins with a couple menders in the middle is quite tough without a way to damage them at range. So if you solo a lot, and are sticking with just 2 weapon slots, go for Supernova; otherwise Polaris is ultimately the better choice.

..Oh, and Supernova kills Quicksilvers better than Polaris.

@HmDepot Not sure if the 500+ can be confirmed on its charge attack (would've thought it to be more), but my Glacius will do 635 for (a very wide) strike and ~170 for the explosions that follow its charge, not to mention freezing the buggers in place for a 2nd charged hit

--edit: This is at depth 24.