I like the Antiguas when I'm still wearing my Wolver gear. They offer 2 benefits over Blasters:

1) They need very few, if any, bonuses to work very well
You can invest nothing into boosting your gun damage and still perform adequately. This lets you go with sword/bomb specific armor sets, instead of the status vulnerabilities of chaos/BK. Admittedly in FSC, a lot of people here could go in with Proto and survive just fine, so it's not that big of a deal. However with missions like GitM, I prefer taking an AP and going all in on Shock immunity. Same goes with C42 and my Sentenza. Heck, my generic shadow resistant loadout invests heavily into swords and DBB, with an AP tagged on with almost no bonuses.

2) They don't cause knockback
Going back to "wearing my Wolver gear," having a gun that doesn't cause knockback is crucial for a sword-focused build. It lets you reliably pull aggro, especially when dealing with large numbers of slow Zombies. Repeatedly tagging something with a blaster will, at minimum, keep it in place, while a swordsman would want to close the distance.

That said, I never use my Gilded Griffon or Obsidian Carbine, and I barely touch my Sentenza outside of C42. Furthermore, with FSC specifically, you'll want Chaos for the Blitz bonuses. As stated above, Antiguas don't need the bonuses that Chaos offers. Maybe if the Antigua charge was just the bird, instead of the stream of shots, then charge spamming Antiguas would be more viable. As of now, CTR is basically worthless on Antiguas.

My short list of good shadow guns is totally different: Winter Grave, Umbra Driver, and maybe Grim Repeater. Basically because they kill.

@Bopp

For what it's worth, the Winter Grave would actually be the next best Shadow gun on my list (tied with the Sentenza, granted, but still), as the flinching on its regular shot lets you deny Darkfang Mender's healing/reviving shenanigans, keep some Thwackers out of commission for a bit and make Gremlin Demos an absolute joke, all the while the charge shot lets you outright 1-shot Darkfang Menders before they even have the time to clutch an Energy Dome (which is the weakest part of the Winter Grave's matchup against them) and absolutely demolish any Lichen Colonies worth their rock salt through a deadly mix of massive multi-hit burst damage and practically-guaranteed Freeze applied to them (or getting flung halfway across the room if they somehow don't get frozen in the process).
However, the regular shot does nothing to prevent Jelly Cubes from instantly spawning their Thorns underneath you, and you don't get enough leverage out of the flinching itself thanks to one of the quickest flinching animations and a primitive AI that's easy enough to kite regardless. Furthermore, it has one of the worst matchups against Stalkers and especially Mortafires, and in no small part thanks to its combination of one of the lowest clip sizes and an inability to move while shooting that make it hard for the user to adapt to the twitchy behavior of those two; in fact, the Winter Grave is actually broken against Mortafires, as the flinching on its regular shot stopped working on a sadly consistent rate against them after I shot them a few times. Lastly, if it handles Darkfang Menders like no other gun, you'll be hard-pressed to properly using it while 12 Thwackers are hot on your heels; sure, you can pop off a charge shot and insta-kill like 5 of them at once, or even aim at one of the two Menders and kill it that way, but good luck being able to pull any of them and not get severely hurt in the process (oh, and did I mention that the Menders can dodge the charge shot? Because they can, they likely will, and you will feel like an idiot watching your shot hitting jack while the 12 Thwackers are already getting their hammers fierce for impact).
The gun is basically overkill at the cost of you getting overwhelmed quickly. In fact, all the weapons you mentioned are overkill for what they're meant to be used against: If both Gremlins and Slimes are indeed bulky, the danger they pose to you actually lies in the ability for them to overwhelm a knight who can't keep up with their shenanigans, whether that be bulk healing, reviving, area denial in the form of bombs/thorns, shields, dashes/dodges and all other sorts of clutch abilities. A weapon is a tool, and a tool is only as good as what it can do for what its purpose is meant to be; if a Shadow gun can't let you adapt to what Gremlins/Slimes might pull on you, then it's not good enough for its purpose. If I can't solo a Gremlin Arena/OCH/Shadowplay/C42/Literally-any-other-place-where-Gremlins-are-the-deadliest without having to throw Sparks of Life into the mix, then what I have on me isn't good enough for what I'm facing.

@Ze-Epic

Same deal here with the other Shadow guns mentioned; pure overkill (turned up to 11 in this case, in fact) at the cost of getting overwhelmed easily. The only matchups the Blitz has that are superior over any other Piercing gun are Alpha Wolvers, Trojans, Vanaduke and possibly Chromalisks and Silkwings. Nevermind the fact that you'd get quickly surrounded by 12 swooping Greavers simply because you stopped moving for a bit (even if you were to prevent some of them from attacking you with one regular salvo of needles), Devilites and especially Overtimers will laugh at your predictable attempts to one-shot them, easily dodge most of it, and fling stuff right back at you before you have the chance to pull back your shield (if it wasn't already broken in the first place for you being the human personification of a sitting duck). Oh, and good luck pulling your shield up anytime soon if you ever get stunned by the above-mentioned before you finish reloading. And you just can't forget all those times where you got bitten by Gorgos/Wolvers while you were killing a few of their kin; totally worth it, amirite?
Honestly, I'd rather take a Volcanic Pepperbox with me to FSC; if its charge shot technically deals less than half the damage a Blitz does to Vanaduke, it's still a buttload of damage for one charge shot, it still insta-kills T3 Elite Trojans, AND I get the added bonus of actually being able to use it elsewhere thanks to the amazing knockback on its OP charge shot making it much safer to use even in risky situations.
Hell, I'd rather bring my Callahan back from the grave than use a Blitz Needle on Fiends; they don't deserve that kind of respect, and they never will in my book.

@Bopp

Well, as an old-school pure Gunner (by which I mean I rarely use my Battle Sprites in-battle even when I should), my second weapon is either going to be a gun that's effective against the secondary type of mobs I'll find on the stage (AKA if Deconstruction stage pops up, bring out an elemental gun alongside the usual shadow gun for the Constructs), or one that, together with my first gun, can give me good all-around matchups based on my personal priority list and/or what the stage might throw at me (AKA not bringing a piercing gun on D&N because of a notable lack of Fiends or bringing a piercing gun instead of an elemental gun on a Gremlin/Construct Compound because the stage title implied Dust Bunnies).

I don't necessarily prioritize how each one of my weapons work with each other so much as prioritize what I can get out of each one, given the usual limitations (solo elite runs, 2 weapons, no trinkets, generally mediocre luck with healing items/vitakits), and if it's enough to work in my favor against the very worst the game could possibly throw at me (Ex: Can this piercing weapon handle Devilites, Gorgos and hordes of 12 Greavers well? Yes? Great! I'll take it even if it'll take me longer to handle Wolver packs with it. Can I find a weapon with better matchups against Beasts but without compromising my Fiend matchups as much? Possibly even better, but if that small compromise is just enough to tip back the scales in the Fiends' favor, then I'd rather take forever to kill Wolvers than horribly dying to Fiends), if you can see what I'm getting at here.

At the end of the day, though, it's nothing more than a painful process of trial-&-error. Throughout the years I played this game, I have dabbled in almost every single handgun family not named Mixmaster (from the rather justified but still overrated Blitz Needle, to the kinky but still underwhelming Callahan, to the deceptively worthless Hail Driver, to the laughably overspecialized Biohazard, to the one true Anti-"4x4 Turret Room of Death" Polaris, to the exceptional Riftlocker, to now), and I'd always try to bring out the very best out of each by practically throwing them against the most nightmarish situations I ever was and could possibly ever be. Are the results foolproof? Not one bit; not only have I not yet experienced every single situation the game could potentially put me in, but I also know by gut feeling that some situations are just so downright unfair by raw level design alone that even the best weapons I could possibly get would only get me so far in those specific situations (Compound levels with the mini-mob spam at their end and the Herex boss fight on Shadowplay come to mind; "Let's just throw in Dust Bunnies, Mecha Knights, Gun Puppies, Mortafires, Darkfang Menders, Thwackers AND a Stalker-like Miniboss onto a cramped room at the very last point of a mission where you first expected and since fought nothing other than Undead and some Fiends").

Though I believe my matchup experiences as a pure Gunner are somewhat worth sharing, they are still just my own experiences; if you can afford to use a Grim Repeater because you have the backup of an Acheron, then that's a fine and dandy cup of tea you got there. It's not my cup of tea, but it's yours, and if it's tasty enough for you, then I can only agree to disagree at worst.

@Ze-Epik

Trust me, if there was any other elemental gun that was just as reliable as the Polaris in terms of flinching all variants of the 12 Gun Puppy/Howlitzer/Polyp rooms you can find in Danger Rooms and even Arenas, I would've taken it instead. Though I like how it can deal very similar damage to the Arcana, I don't particularly like the Polaris' slow hitbox and its "can't do much at close-range"-ness in the face of Kats, Deadnaughts and even Mecha Knights and Scuttlebots, of all things.

Mind you, the matchups are still workable with a Polaris, but thanks to said mobs being slightly faster than their kin at approaching you (even if they're just as predictable once you know what to expect from them), the matchups are particularly awkward to face as you kinda struggle to find enough range between them to hit them with anything but weak shots every single time.

Still, I'd rather take those awkward matchups than having to face true bullet/missile hell, and as a solo runner, the gun's notoriousness in group runs, if very justified, matters very little to me, which is why the Polaris is my elemental gun of choice and why I still consider it to be the best elemental gun in the game. Close seconds though would have to be the Storm Driver and possibly the Nova Driver (if its regular shots are powerful enough to consistently flinch turrets on hit, that is).

I think most ppls choose Arcana over Argent for some reasons:

- Single-switching Arcana would have more DPS (2-shot/switch)

- Spamming Argent on tanky slags hurts your fingers

- Arcana has a larger bullet hitbox, meaning you have more opportunities to hit 2 or maybe 3 targets at the same time, argent can also hit 2 targets at once but it would require the targets to be extremely compact with each other.

- Both Arcana and Argent are mostly used as sidearms (pair with swords) and rarely as main weapons. Arcana has a knockback which is useful for sword-main gear.

I play as a gunslinger like 4/5 of the runs, always playing with max dmg, VH-Max CTR/ASI.
My Carbine is just sitting on my inventory since my Umbra Driver and Winter Grave does the job better against slimes and gremlins. Carbine's rival would be Phantamos which also sits on my inventory... But I will say Phantamos for slow tanky slimes and Carbine for squishy/dodgy gremlins with gremlin mender.

I have an argent peacemaker before but I sold it when I felt my new Arcana does the job better as a sidearm (When I play with swords). Arcana is also nice as a main elemental weapon but not as good as alchemers. Also some elemental handguns other than mixer can be outdpsed by some normal/shadow handguns like a Charge-oriented Wintergrave/Grim for constructs, Iron Slug for both ghost and constructs, Pepperbox for slags and constructs.

I think that if Iron slug's charged bullet knocks back targets properly... most elemental handguns would be easily outdps most elemental handguns... and would be on par with brandish spams.

I don't have much opinions on Gilded Griffin since I never had it, I think it would do its job well against fiends but I think it would not be as good as other pierce guns like Riftlocker, Callahan, and Blitz.
-Gilded griffin would be safe to use on tight rooms with devilites but it would also make devilites dodge more than riftlocker, and it lacks knockback which is useful against greavers and gorgos.

-Riftlocker has almost the same purpose with Griffin, except that it has more dps, and has a knockback which can counter greavers. This is my bread and butter on fiend levels.

-Callahan can stagger a target in a single shot, which can counter greavers easily. Single-switching it against devilites would easily stun lock them in place to death. Its charge attack is my favorite against a group on greavers, especially on fiend arena. Also useful for sniping silkwings ith its charge attack.

-And ofc Blitz Needle's charge attack would easily takeout these fiends especially tanky pit bosses as long as theirs lots of opportunities to steal 3-5 seconds w/o getting hit. Its also very useful for taking out monsters after spawning them.