Dual wielding has been a largely talked about idea for a long time. Despite how "cool" it would be to have two weapons, it has been rejected many times because of the unfair advantages that it gives players and the chaos that it would bring to the way this game works. I just doesn't make sense how it can fit into a games like this one. However, while a knight holding two separate weapons (example, a Flourish and a Cold Snap) wouldn't make any sense, combining two very similar 4* weapons together (example, Blazebrand and a Blizzbrand) could permanently create a single 5* weapon. Weapons would have the same attack power as the 4* weapon so not to be too strong. Weapon combinations will be explained below. I also decided that dual bombs didn't seem to really work in any way so there is not a segment on bombs.

Swords:
Remember that what is being created is a entirely new sword. Just because two swords got combined does not mean that they should get double attack speed or double attack power. My suggestion would be that average speed swords (such as Brandish and Calibur lines) just attack a little faster and get 2 more attacks to the combo. Dual Caliburs charge attack is a 360 spin with more reach. Different Brandish (example, Blazebrand and Blizzbrand) charge attacks should be 4 lined-up, large explosions that alternate in effects (example, fire, ice, fire, ice). Same brandish (example, Dual Boltbrands) charge attacks would be 2 columns of 4 explosions. The Dual Flourish/Dark Thorn Blade combos would be the same, just with faster execution. The charge attack would be on long stab forward with both swords. Thee Dark Thorn blade charge would be a 2 slashes (one with each sword) with each slash followed by a phantasmal image of the Snarbolax biting. Here is a list of sword combinations that would work.

-Blazebrand & Blizzbrand
-Blizzbrand & Boltbrand
-Boltbrand & Blazebrand
-Dual Blazebrands
-Dual Blizzbrands
-Dual Boltbrands
-Dual Silent Nightblades
-Dual Ascending Caliburs
-Dual Cold Iron Carvers
-Cold Iron Carver & Ascending Calibur
-Grand Flourish & Daring Rigadoon
-Daring Rigadoon & Fierce Flamberge
-Fierce Flamberge & Grand Flourish
-Dual Grand Flourishs
-Dual Rigadoons
-Dual Flamberges
-Dual Dark Thorn Blades
-Dual Winmillions

Guns:
Dual gun are a little less complicated then dual swords. Basically dual guns will be shot by alternating between both guns until both are out of bullets and are reloaded together. Dual guns would give lose having a charge attack altogether, instead holding down the attack button will just make you fire as fast as you can. A single press with just make you gun shoot once. Also gun will become about 10 to 20% weaker per shot depending on what the spiralknights staff decides if they take this idea.
-Dual Prisma Drivers
-Volt Driver & Firo Driver
-Firo Driver & Cryo Driver
-Cryo Driver & Volt Driver
-Dual Volt Drivers
-Dual Firo Drivers
-Dual Cyro Drivers
-Dual Shadow Drivers
-Dual Silversixes
-Dual Blackhawks
-Dual Mega Magnuses
-Dual Master Blasters
-Dual Volatile Catalyzer
-Dual Virulent Catalyzer

When creating the dual weapon is created the 2 original ones will be destroyed. This process should be very hard and expensive so that dual wielding is limited to only people who are will to do the hard work or purchase energy. It should require both combined weapons to be level 10 and at least double the amount of alchemy orbs it takes to create a normal weapon. A dual weapon upgrade that expires in 30 days should also be required to wield any dual weapon of any kind. Wielding a dual weapon will cause your shield to get replaced by a weapon and you have to switch to another weapon to use your shield.
I hope you consider my idea!