So the Flingza's been discussed a lot, and as a vanilla Flingza 'main' (not really a main but it is the weapon I'm most comfortable with, along with the Inkbrush), I have to throw in my two cents.
People underestimate the Flingza because its mechanics aren't explored properly. Its horizontal flick is objectively worse than the Splat's (though only by pixels thanks to 3.0.0), while the vertical is slow, has falloff so massive that you're usually dealing the minimum 40, and is lower ranged than the Dynamo to boot.
But tag someone with the vertical for 40, and the killing area of the horizontal flick becomes easily better than that of the Splat. Glance them with a horizontal, and you can back up without them giving chase - if they do, a vertical flick should do it. Or sneak up, and then just a horizontal flick or roll will work.
Peek onto ledges with the horizontal, or peek around obstacles with the vertical. Use the horizontal to fix up patchy ink, or use the vertical to paint swathes of flat land.
Take down Inkjets, pop or delay Ballers, jump onto Bomb Rushers and Stingrays or distract them, keep Bubbles in check, pressure them into using Splashdown uselessly, remove Ink Armor, and paint over Ink Storms. Positioned correctly, it can literally counter every single special in the game.
It's a Tactician's weapon through and through; a swiss-army tool. It even flips into different shapes!
The sub and special, despite seeming like the oddest choices possible, help immensely too.
The Splash Wall protects against long-ranged weapons and stalls them, making them ripe for splatting. For short-ranged weapons, it's exactly what it says on the tin - a wall. Toss it down and vertical flick immediately. If they notice it coming and swim through before the wall can come up, the vertical flick will kill them. If they don't, they have to either swim round it (go under the wall and horizontal flick them), attack it (you can attack them directly), or run away. Or you can just hand it off to teammates - Splatlings work best for this - and flank the enemy while they're dealing with the more obvious threat.
Splat Bomb Launcher is almost overpowered. Where most weapons retain their main attack while using a Bomb Launcher, the Flingza retains its main attacks, plural. Two indirect bomb hits and a long-range vertical flick is a kill. One indirect bomb hit makes the killing range of the horizontal flick much better. Plus you retain all the normal killing methods, and can just bomb spam.
Pack Thermal Ink, 3 subs Bomb Defense for countering Splashdown and Baller, Ink Saver Sub for the Wall, Special Charge Up for the Bomb Launcher, and maybe Sub/Special Power Up. I use Run Speed for the vertical flick, but I'm not sure if that even works so don't take it into Ranked without tests.
Hardly anyone uses the Flingza, but I have to ask why. It was good enough with the damage holding it back; now with a better horizontal flick and the buff to both the Splash Wall and Thermal Ink, I'm sure we'll see much more... of the Foil Flingza.
Joke's on them.
As for the new weapons:
Neo Splash-o-Matic must be an Attacker/Controllor weapon. Burst Bombs combined with its accuracy make it great at kill-confirming, and all of its kit, including the Suction Bomb Launcher, is great at painting turf and denying enemy positioning.
Foil Squeezer would be Tactician, I think. It's versatile to begin with, and the Splat Bomb/Bubble Blower kit is very similar to the Forge Pro.
New Squiffer - Attacker/Carrier. Autobombs keep it aware of enemies near the objective, and the main is a quick-charging one-shot. Baller lets it kill-confirm, chase enemies down, or stay on the objective unharmed.
Gloogas Deco, I'm tempted to call Attacker/Defender. Splash Wall for stalling and blocking, three/two-shot kills but stationary, fairly long range, and the Baller for escape, and for chasing down enemies.