So in Bleach we have many zanpakuto that we know virtually nothing about and those we dont know enough about and I just thought it would be nice to address the topic.
The Partially Known
Ryūjin Jakka (流刃若火; "Flowing Blade-Like Flame"): The oldest and most powerful fire-type zanpakuto in soul society. Has the greatest attack power of any zanpakuto. The question is what is its bankai? Well so far we have seen it do things with fire simply in shikai that is at the level of bankai for most captains. Even better point would be to ask what could this bankai even be cause it would take the idea of overkill to another level. At this point all I can imagine would be it bringing out a Sun.
Kinshara (金沙羅, Golden Sal Tree): In shikai Kinshara takes the form of a whip and seems to derive its powers for mostly anything related to the music genre. What its full capabilities are unknown but it seems highly versatile in what its capable of achieving. What has been shown hints at a multitude of abilities. What is its bankai? Well thats questionable as what form it would take, whatever it would be should be pretty interesting.
Sakanade (逆撫, Counter Stroke): In shikai Sakanade takes on pretty interesting form. The biggest point is not so much its shape but what it does. It a trump card, as it capable of activating upon release. It causes optical illusions the level of which your mind cant even figure out. Whats its banaki? Well I couldnt figure what would be more powerful then this level of illusion.
Tengumaru (天狗丸, Long-Nosed Goblin): In shikai Tengumaru takes the form of a giant kanabo that can through around fire. Whats its bankai? Your guess would probably be better then mine.
Katen Kyōkotsu (花天狂骨; Flower Heaven, Crazy Bone): In shikai Katen Kyokotsu takes the form of two dao swords. The power they wield, make child games a reality. So essentially changing the laws of reality to specific preset conditions based on children's games with a deadly combative twist. This has to be the most devastating powerful ability out. Whats its bankai, well whatever it is i wouldnt want to be on the receiving end of it. Another overkill situation. I think so. Its hinted at being something that well isnt to be used in situations where you got allies all around to see it.
Tachikaze (断地風, Earth-Severing Wind): In shikai Tachikaze is the form of a combat knife. Its abilities center on different uses of wind manipulation for devastating effects. In bankai Tekken Tachikaze takes on a minimalistic but interesting look. Whats its abilities, well thats any ones guess but guessing it would be even greater wind manipulation mixed with hand-to-hand combat. Typically Kensei.
Benihime (紅姫, Crimson Princess): In shikai Benihime takes on a intricate and heavily ornamental look. What its capable of is something of a manipulation of red energy for a multitude of purposes, both combative and defensive as well as extremely versatile. Whats its bankai, well the hinting suggests something that is highly destructive in nature.
Sōgyo no Kotowari (双魚理, Truth of Pisces): Ukitake is picked for this point cause we have seen him redirect energy and what not but im almost ceratin there is more to what Sogyo no Kotowari is capable of and we arent seeing anything. But then he rarely fights. What his bankai is, well im more concerned about what the shikai can do as opposed to what the bankai can do. But my guess would hinge on it doing a greater version of the shikai abilities we arent seeing.
Engetsu (弦月, Scathing Moon): Engetsu is capable of using a getsuga tensho. We dont know its release command, nor do we know what its bankai is. We do know that it is insinuated to be capable of using the Final Getsuga Tensho.
Gonryōmaru (厳霊丸, Solemn Spirit): little is known about Gonryomaru. Its shikai is apparently the form of a katana/rapier hybrid. Whats its abilities are unknown. What its bankai is also unknown. What is odd is that in the unknown zanpakuto filler arc his spirit was shown and its powers were lightning, whats odd about it is that the arc made sure to say all shnigami zanpakuto were effected but made sure not to showcase any of the zanpakuto spirits of zanpakuto we didnt know fully about, except for Gonryomaru.
- Whatever Yoruichi has its name is unknown. It has never been seen released in the entirety of bleach. What it can do is totally unknown as she doesnt even carry it. This would lead one to infer that it is not fit for her still of combat (hand-to-hand & high speed) or its more supportive if not more destructive or defensive. The book of possibilities are numerous here.
Minazuki (肉雫唼, "Purify the Flesh"): What we known about Minzauki is its name. we dont know its release command nor do we know the full capabilities it possesses. We have seen it form a living creature in the form of a manta ray that can fly and heal people within its stomach. Is this a supportive zanpakuto exclusively or is there more to it. We have little to nothing to go on besides the fact that Unohana has never shown fighting and we dont know anything.
Itegumo (凍雲, Frozen Cloud): What we know about Itegumo is literally nothing. We have seen it released once and it didnt change too much. What its abilities are anyones guess.
- Whatever Ginrei has its name is unknown. Its release command, its form, what its capable of, its all a mystery.
- Iba is interesting a bit. We have seen its shikai form, but dont know its name, its release command or even if it is capable of anything, which is odd.
- Nanao is another thats odd. We havent seen it released we dont know its release command. Thus we dont know its capabilities. Seeing as she has never been seen in combat one might conclude it has no combative capability. It may like she is considered to be purely combat supportive.
Haguro Tonbo (鉄漿蜻蛉, Iron Drink Dragonfly): Lisa's zanpakuto in shikai tends to be a long polearm monk spade deal. What it can do is anyones guess.
- Mashiro has a zanpakuto, what its name is, what its release command or even its capabilities are virtually unknown. Once again the best that can be determined is that it simply doesnt fit her preferred form of combat (hand-to-hand).
- The elephant in the room. Kenpachi doesnt known the name of his zanpakuto, its release command, and he's the only captain that doesnt know his bankai. Will we ever find out anything about this sword. Doubtful, Kubo apparently has no interest in progressing this character or his abilities. Oh well.
- We see her carry it around. we dont know its name, we dont know its release command or its capabilities. What do we know? Nothing. Yachiru never fights and Much like Kenpachi's situation kubo has admitted to putting no effort into development of this character either.
- Nemu is a interesting situation. It is insinuated at least in pics that she does have a zanpakuto though in the entire series she has never been seen with one. Her form of combat is entirely hand-to-hand when we have seen her fight. It begs the question whether she even actually has a zanpakuto, as she is a artificial construct and not a true Shinigami. I would surmize that if she does indeed possess a zanpakuto its probably very similar to Mayuri's as she is essentially a mix of gigai/artificial soul and mayuri's blood.
Kubikiri Orochi (馘大蛇, Beheading Serpent): Hiyor's zanpakuto in shikai looks like an enlarged cleaver with a serated edge. What it can do is anyone's guess.
- Tessai must have a zanpakuto, but he uses kido and never his zanpkauto.
- We have seen Hachi's zanpakuto, but he uses kido and never his zanpakuto.