Weapon swaps are the unique descriptions that come when swaping a weapon, mainly bastard swords from one blade to the next. There are other swappable weapons in the game, and I assume the swaps apply to them as well. So far, barbarians have the most weapon swaps available so I've included this in my section. Weapon swaps are based on blade ranks, dances, berserks and in spells active. I'll list the spell swaps as well since it may be useful to know what spell a pesky mage has up.

Rank Based Weapon Swaps

1-99

You switch your sword so that you can use it as a heavy edged weapon.

100-199

You deftly change your grip on your sword so it can be used as a heavy edged weapon.

200-299

You fiercely switch your grip so that your sword can be used as a heavy edged weapon.

300-399

You effortlessly switch to a grip for using your sword as a heavy edged weapon.

400+

You turn your sword easily in your hands and end with it in position to be used as a heavy edged weapon.

Dance Weapon Swaps

Swan Dance

Your hands gracefully move to grip your sword as a heavy edged weapon.

Cobra Dance

Your hands quickly move to grip your sword as a two-handed edged weapon.

Bear Dance

Your arms flex with power as your hands move your sword into position to be used as a two-handed edged weapon.

Wolverine Dance

With a quiet snarl, you move your hands to grip your sword as a heavy edged weapon.

Panther Dance

Your hands fly to a two-handed edged grip on your sword.

Dragon Dance

Your eyes blaze as your hands move to a two-handed edged grip on your sword.

(There does not appear to be a special weapon swap for Eagle or Badger Dance. It defaults to rank weapon swap)

Berserk Weapon Swaps

Berserk Blood

You grip your sword as a heavy edged weapon to better devastate your foes.

Berserk Stone

Your grip tightens on your sword as you grasp it so that it works as a heavy edged weapon.

Berserk Nightmare

You swing your sword in a sweeping overhead arc as you change your grip to use it as a heavy edged weapon.

Berserk Flame

Through your bloodlust, you sense that you have switched to a heavy edged grip.

Berserk Cyclone

You fiercely grip your sword in a heavy edged grip.

Berserk Grave

Your sword becomes an extension of your bloodlust as you switch to a heavy edged grip.

Berserk Kuniyo

A quick flourish of your sword leaves you gripping it as a heavy edged weapon.

Berserk Everild

You sweep your sword in a deadly arc and in the process switch it to be used as a heavy edged weapon.

Berserk Trothfang

A roar rips from your lungs as your hands grip your sword to best wreak destruction with a two-handed edged grip.

(There does not appear to be a special weapon swap for berserk steel. Default to weapon rank swap.)

Warrior Mage Spell Weapon Swaps

Sure Footing

Stepping into a perfectly balanced posture, you adjust your grip on your sword so it can be used as a heavy edged weapon.

Mantle of Flame

Your fiery mantle sends tongues of flame licking along your sword as you shift your grip so it can be used as a heavy edged weapon.

Swirling Winds

The winds of Elanthia guide your movement, effortlessly shifting your sword so it can be used as a heavy edged weapon.

Ranger Spell Weapon Swaps

No spell up

Your hands seem to glide upon the surrounding air as you agilely adjust your grip on your sword so it can be used as a two-handed edged weapon.

Senses of the Tiger

With cat-like grace, you languidly shift your stance and grip your sword so it can be used as a two-handed edged weapon

With Claw of the Cougar

Poised like a cougar preparing to pounce, you swiftly grip your sword so it can be used as a two-handed edged weapon and stand ready

Thankyou Yuoree, Tropicalo, Simon, and Rikulf for the help of gathering this information.