Kind of stuck choosing on my character's zanpakto's ability.  So was wondering if anyone had any opinions on these
The ideas I have are:

*Nano-bots: At first glance the shikai won't look much different from Byakuya's or Rangiku, but instead of tiny shards that can rip a person to pieces, the pieces will actually be tiny robots which can form together to create various weapons or devices.  The little bots can't interact directly with anything except for each other or Jynmi(just drawing power from him).  The bots will be incapable of duplication.  
^* The bankai will be almost the same but the bots will be even smaller in size, capable of duplication, and will develop small claws which are immensely strong that will allow them to manipulate the world around them at a sub-atomic level.  

*Vacuum The shikai will be able create and manipulate long black flame like winds which are actually complete empties.  IE Kenokinesis.    
^* Not sure exactly about the bankai but it will grant the user the ability to create a field of a certain size and the user will be able to multiply various natural forces within the field.  

*Frankenstein- Sort of like Retu's ability but instead of a giant mantarey like creature there'll be a heavily muscled, humanoid figure with the ability to control any limbs separated from the main body though damage to the head and chest is taken normally
^*Not sure what the bankai would be for this.

(Note, nothing has been settled on, these are just the ideas I've been playing around with the most.  So if they seem Op or need to be buffed, nerfed in some way I'd be happy to hear it.)