Ecchihentai

Ecchihentai (lit Lewd Pervert) is a Zanpakutou created by Cyberweasel89, but open to be used by others.

Sealed State
The Zanpakutou is sealed as a seemingly ordinary katana. However, the katana has a gauge attached to the hilt, similar to a speedometer.

Sealed State Abilities
Ecchihentai is very unusual, in that it possesses abilities even in Sealed State. If the opponent is cut with the sword, and as long as some of the opponent's blood remains on the blade, the wielder can change the opponent's gender by saying the command "Arouse". The Shinigami can change the opponent's gender as many times as they want by saying the command again, so long as the blood remains on the sword. The benefit of this is that a Shinigami will be unused to their body as a different gender. They will likely be unable to achieve the same level of balance and grace as they would with their original gender.

The gauge on the hilt measures the user's arousal in the same way that a speedometer measures speed, and functions in the same way. If the user is calm, the arrow on the gauge remains on one side, in the green. But as the user's arousal rises, the arrow on the gauge moves from one side to the other, going from green, to yellow, to red. The purpose of this is that the Sealed State is actually quite weak at first. The edge is dull, the structure is fragile, and it feels heavy to the user's hands. But as the user's arousal level gets more intense, the more the gauge climbs to one side. And the farther the gauge is, the more powerful the sword is. As it climbs higher, the edge becomes sharper, the structure becomes tougher, and feels lighter in the user's hands, while still striking hard. At max, the sword is sharp enough to cut through another Shinigami's Sealed State, the blade becomes almost indestructible, and the sword feels as light as a feather to the user.

Shikai
The user cannot activate Shikai at will. The gauge on the Sealed State's hilt must be at max. When the gauge is at max, the user can activate Shikai with the command "Get It Up". At that point, the gauge melds into the sword, which becomes thinner and grows a hook on the end.

Shikai Abilities
As long as some of the opponent's blood remains on the blade, the user can say the command "Strip" to make a random article of the opponent's clothing disappear. The command can only be repeated once every three minutes. The purpose is actually strategic, as an opponent will be too focused on their nudity to fight efficiently, thus giving the wielder of the Zanpakutou the edge.

The Shikai of Ecchihentai can still change an opponent's gender with the "Arouse" command.

Bankai
The Bankai is called Shitagidorobo Ecchihentai (lit Underwear Thief Lewd Pervert). Only once the opponent is completely naked can Bankai be activated. When the opponent is completely naked and the user says "Bankai", a large explosion of light engulfs the user. The user is then seen riding atop a giant monster with many, many tentacles.

Bankai Abilities
The Bankai summon emits a pheromone that acts as an aphrodisiac. The aphrodisiac pheromone will render the opponent with thoughts so clouded that they will be too aroused to concentrate on the battle. The battle is won when the user is able to pick up the opponent and feed them to the Bankai summon's mouth.

Zanpakutou Spirit
The Zanpakutou spirit is a dirty old man of small size with a large bundle of women's panties in the bandana strapped to his back.

Trivia

 * The name of the Zanpakutou can also roughly translate to "Lewd Transformation", which fits with the Zanpakutou's abilities.
 * The Shikai of the Zanpakutou, which resembles a thin rod with a hook on the end, is similar to a tool used in a prank between elementary and middle school students in Japan. The hook on the end of the stick is used to pull down an unsuspecting girl's skirt from behind.
 * The Bankai of the Zanpakutou is reminiscent of the common female fantasy and common anime pr0nagraphy act of "tentacle sex".
 * The aphrodisiac pheromone that the Bankai produces categorizes the Zanpakutou as a Poison-Type.
 * The Zanpakutou's spirit resembles the character of Happosai from the anime and manga Ranma 1/2.