Hello, still relatively new to the game here, though I've played extensively since I hoped in.
I certainly don't have any view on the past deeds of weapons but I've tried all of them both as a gunner and a captain, here's my thoughts in a nutshell
-small weapons :
harpoon : tried it whenever it was available on a ship, added it on my setup a couple time. People seems finding a bit hard to hit with it, I suppose it's because of relative inexperience with it, so I can't really tell about the damage. The tow line on itself doesn't seem to control much, I think it can be a good thing only if you want a quick little fellow to stay with you.
flare gun : encoutered a bit, can't say much about damage. utility is perceptible on some maps
These two utility guns are really rare, but it's certainly mainly because of the lack of gun parts, so it's always hard to put one. Though some ships have arguably guns that are seldom used, so it' doesn't hurt much.
mercury/small flack/small mortar/small caronade/minigun/artemis : I think all these weapons are fine and play their respective role quite well.
flame thrower : I haven't lived through the day of infamous fire damage, currently, even if it's handy as a side gun, it doesn't seem to provide anything stellar. Artemis or caronade are good disablers that have a direct impact on crucial parts. As an escape weapon combined with tar, maybe... I dunno if there is a solution without making it overpowered. Maybe tweak damage matrix of fire to make it a bit more specialized.
carrousel : Just never seen the impact of this weapon. Seems to fit a niche between artemis and small flack? The projectile have some nasty dispersion and the overall effect is hard to judge. I don't see what is expected from this gun. Maybe it could work as a mini manticore, with more of a "barrage" mechanic.
- medium weapons
Lumberjack : I respect the weapon though it needs a decent gunner. Seems to lead to a bit boring gameplay, alas, as you want to stay away and pound a ballon deprived ship.
Twin caronade : a fun choice, less safe than the lumberjack but definitively has a role
Manticore : honestly this one seems overused, but it's easy to understand why, for it's the best disabler, does decent damage overall, needs only a small window of opportunity. Plus game wise it's impressive and fun to use, as no over weapon gives the "barrage" feeling. It's no wonder most goldfishes I see are sporting it, as it crippling power make it the "best" lone medium weapon.
Typhon : I have an issue with this one. It's the gun with the nearest "old artillery" feel, and it's quite hard to use at a distance with relative speeds. And when you manage to get your hits, you can't expect much unless the armor has been removed for you. So I guess in the hand of a decent gunner, and if you're running a combo with another ship/armor shreading guns available. Issue is the hull will often be removed when ships are closer and then you'd miss the secondary. I've seen and performed kills with a typhon, but it needs a perfect window for use. All over medium weapons have a crippling effect that this one lacks. In the end, it boils down to the feeling that you've not granted much for those difficult long distance shots, whereas with a mercury I get the feeling I'm really putting the enemy through an hard time, wrecking armor and parts in a precise manner. And if you end up in medium range, why not use manticora or lumberjacks anyway?
Of course it may be all a biased feeling and specialized weapons are more powerful when used with combined fleets, but most of the games are quite chaotic. I like to experiment with weapons but so far typhon and carousels are kinda letdowns for me.