Well then I got a rather good one written up.
It's still in the experimental phase, might make a few minor to major changes until the final version. Would like some feedback until then.
I'll just leave most of the names as english, I already speak enough Japanese on a daily basis as is, and considering how I've been up all night I'd likely butcher it to heck and back.
Also I'm a gigantic fighting game buff and fan of the Fate/ series so I'm probably gonna get real technical with stuff here so bear with me.
Zanpaktou Name: Kuro no Ryu (The Black Dragon)
Type: Fire, Sound, Darkness
Zanpaktou Spirit: True to what the name implies, Kuro no Ryu takes the form of a black dragon. More akin to a chinese serpentine dragon. It's body is wreathed in purple fire.
Release Command: "Rock, Kuro no Ryu!" (socreativesuchreleasemuchdoge)
Shikai Details: Kuro no Ryu transforms from a standard katana into a jet-black Gibson SG electric guitar additionally, the soul reaper (Let's call him Raidou for now until I think of a different name) gains a cloak of purple fire.
Dragon's Sacred Wings:
The cloak of fire as several effects. Firstly, it offers strong resistance to attacks based around the usage of spirit energy. (ie Kido, cero) because it is a cape, however, it has to be moved accordingly to shield vital parts. While not offering full protection, it absorbs a portion of spirit energy and converts it into Black Dragon's Fire. Not effective against strong spiritual attacks, at base form only reduces damage by roughly a quarter. Maintaining Dragon's Sacred Wings consumes spirit energy over time, but can be toggled off and on by playing a tune on Kuro no Ryu.
Black Dragon's Fire:
The "ammo" of this zanpakuto. Black Dragon's Fire is spirit energy converted from Raidou himself or from attacks against him. Black Dragon's Fire allows raidou to enhance his attacks and fling orbs of dark flame by playing Kuro no Ryu.
Poem of the soul:
Raidou plays a supportive song on Kuro no Ryu, converting spirit energy into either an ally or himself.
Bankai Name: Kuro no Ryujin (Black Dragon-God)
Bankai Details: Kuro no Ryujin provides a large spike in power, greatly increasing the limited pool of abilities provided by Kuro no Ryu.
The first change is Kuro no Ryujin's ability to switch between two forms. The first is a large black zweihander, roughly a foot wide and 8 feet long, brought to a triangular point at the end. The hilt itself is a foot and a half long. The second is similar to the shikai, is a Gibson EDS 1275. (which is a double-neck guitar)
Dragon-God's Blood - Fafnir:
Replacing sacred wings is Fafnir, a suit of pitch-black full armor. Constructed of interlocking pieces to provide the highest possible movement. The armor covers his entire body, save for a leaf-shaped hole on his back. Purple dragon's fire blazes around it. The difference in power between Fafnir and Sacred Wings is Fafnir's uncanny defense. Physical attacks against the armor are completely negated. Spiritual and ranged attacks are absorbed and converted into Black Dragon's Fire. (note: similar to the shikai variant, particularly powerful cero, kido, and spiritual abilities can circumvent the armor and cause damage. The more spiritual energy pumped into the armor itself, the stronger it becomes)
Any attack directed at the leaf-shaped hole in the back breaks Fafnir, and a large amount of spiritual energy must be recollected to reform it.
Dragon-God's Great Fire:
An improved variant of Black-Dragon's Fire.
Dragon-God's Maw - Dahaka:
Kuro no Ryujin's sword-form is thrust into the ground, created a large eruption of earth and dark fire. Can be directed in a line, or spread from the center in a large area.
Dragon God's Dread Wings - Wyvern:
Kuro no Ryujin forms wings of purple fire on the soul reaper's back. Flying through the air at a high speed, Kuro no Ryujin rains down fiery destruction before hitting the opponent with a sword-thrust from the heavens.
Dragon God's Endless Thirst - Dracul:
This skill is an extremely risky close-range attack. The soul reaper grabs the opponent and directly saps their spirit energy. As stated before, must be within extremely close range, backfires if used on beings with particularly powerful spiritual energy. Can be used on any being containing spiritual energy. (ie: minor hollows, etc.)
Dragon-God's All-Consuming Hellfire - Smaug:
Unleashes a gigantic torrent of Dragon's Fire. Expends all current dragon fire, and reverts to Kuro no Ryu.
Song of Fire:
Plays a song on Kuro no Ryujin, envelopes an ally in Black Dragon's Fire for protection for a short time.
Rock You!:
Plays a song on Kuro no Ryujin, blasting opponents with waves of sound.
Anything Else:
http://en.wikipedia.org/wiki/Gibson_EDS-1275
This zanpakuto is very dragon-themed. Containing such dragons as Ahzi Dahaka, Fafnir from the "Niebelunglied" (probably misspelled it) and Smaug from Tolkien's "The Hobbit"
Rock you! Is a reference to the words inscribed on Sol Badguy's headband from Guilty Gear. Plus it's just Japanese cheese, and that's the best kind of cheese.
I had some trouble with this one, but I tried not to make it very OP. still seems a little OP in my eyes, ah well, that's what contructive criticism is for, fire away!