As a Spiral Knight, your primary weapon is in fact, the sword. You start with it pulled out, and it's something that does the most respectable damage in your arsenal.

FAQ.

Q1: Why Swords?
A2: Every civilization in history has used at least one kind of sword. You have the Greeks, the Romans, Middle Eastern Civilizations, Asian Civilizations, and of course, the Knights of the Middle Ages. Though sadly today Swords no longer have that big of a part in warfare, it's still used for ceremonial purposes and certain sports such as Kendo and Fencing.

Of course in Spiral Knights, Swords are all too important to abandon.

Q2: Why bother with Swords when I can use Guns?
A2: Well for one, guns simply cannot deal the amount of damage Swords can. Yes they're often safer, but often times you may find wolvers, devilites, and gremlins most likely to dodge your every attempt to shoot.

Q3: Is equipping swords only practical?
A3: Of course its practical. You have various different swords capable of achieving different effects. The Avenger/Faust/Spur series has a charge that can shoot projectiles. Calibur/Cold Iron series has a 360 charge attack that has epic knockback. And best of all, they can be used in close combat if you so desire. However there are very few Swords that can inflict statuses and qualify for Endgame material such as Vanaduke. In that case I suggest you get a gun.

Q4: People keep telling me that I should have at LEAST one sword in my inventory of guns/bombs! Should I?
A4: Well it depends on what guns you use. If you're using an autogun, you may want a close range sidearm to fall back on in case something gets close to you while shooting. If you're using an Alchimer or Antigua, you should be fine without a sword, but beware of the reloading.

However you should have a sword if you intend on fighting the Jelly King. The small jellies will block majority of your shots from guns. Bombs may or may not work against him depending on the blast range. If you have a 5* bomb, the range is great enough to effect every jelly and the King.

Overall I would agree with them. Just make it a decent sword you pick.

Q5: What is the best UV available for Swords?
A5: Well it depends on what sword you're using. You obviously wouldn't want a charge reduction time on a Faust if you intend on not using the charge often. Damage Bonuses vs an enemy type is popular these days. Most people would like their weapons to kill the undead... Unless it was a Faust or something more Shadowy.

However you'd best get a Maximum bonus. A low barely helps anyone.

Q6: What status effects compliment the sword user most?
A6: Well I personally love Ice. Ice can keep an area of enemies still while you kill off a few at a time. I personally dislike fighting multiple enemies at a time. Also when enemies thaw about naturally (as in, don't hit them. Let the effect wear off), they'll take pretty good damage. Of course Ice cannot be found on any sword BUT the Iceburst Brandish (3*).

Fire's Damage Over Time is kinda not that great and that's all fire has going for it. Hot and Searing Edge are low end fire swords. Fireburst Brandish can only inflict fire by Charge and lacks elemental attack. Fang of Vog is the only fire sword above 3*.

Shock has a much lower DOT but they may be shocked (paralyzed by the shock effect for a few seconds). They cannot attack or be knocked back, so take advantage Calibur users!

Curse is a great effect on enemies, not so much on the player. Faust's charge is a double edged sword that can curse everyone. For the player, it "curses" 1/2 of your weapons and vials, severely limiting your tactics. Unless you like cutting yourself, I suggest NOT bother using any of the cursed items... unless the Remedy Capsule is cursed, then use it and endure some pain.
For enemies, when they attack, Curse does damage. Faust/Gran Faust are the only weapons capable of Curse.

Poison is great. It lowers enemy attack power and their defenses. It also prevents them from healing. Vile Striker/Dread Venom Striker are the only swords capable of Poison.

Stun slows enemies down. It's not that great of an effect. So far there aren't any enemies that constantly outrun you the the point of being impossible to kill without stun. Troika Series, Beast Basher, Thwack Hammer's charges can inflict some stun.

Some swordplay tips.

Shield Canceling: After your 2nd slash in a combo (1st slash for a Slow Sword, 4th hit for the Cutter series), press the shield button. This will pull up your shield in case enemies aren't knocked back by your attacks.

Charging without slashing: While shielding, hold down your attack button, then let go of your shield. You should see that you're already preparing to charge your attack. This can also work for Bombs and Guns.

Armors/Shields.
The Wolver Gear is the only armor made to cater to sword masters.
From 2-4*, Wolver gear gives a damage bonus low to swords for each piece of equipment, totaling to a medium damage bonus.
But at 5* the series splits into Vog Cub, and Skolver set.

Skolver offers...
Normal/Piercing Defense
Damage Bonus Medium for each piece (Total = Very High damage bonus)
Freeze Resistence

Vog Cub offers...
Normal/Elemental Defense
Attack Speed Medium for each piece (Total = Very High Attack Speed Boost)
Fire Resistence

For me, I'd get Skolver for PVP considering you'll die quickly in there anyways, but Vog Cub for survivability due to elemental defense's importance.
Most armors don't cater exclusively to swords the way Wolver set does.

Now for shields, you really only have two options if you want something other than defense.
You have the Scarlet Shield and the Swiftstrike Buckler.

Scarlet Shield gives +2 HP, and has Elemental and Normal Defenses.
Swiftstrike Buckler has an attack speed boost high, and gives very little defenses.

Neither of these are good for survivability in Tier 3, but they're good in Tier 2 and PVP.

Trinkets trinkets trinkets...
No longer are there attack speed trinkets or damage boost trinkets as there once was in CB.
The resistances and defense values gained by trinkets are often minimal, even at 5*.

I suggest getting Heart Pendants, which are exclusively dropped (sometimes) by Love Puppies, a rare harmless variation of the Gun Puppy.
They add HP to your total value.
The 5* version gives you +6 HP.

They're rare but you can find people willing to sell these babies for often high prices.