There is a construct I am quite fond of in pointer-friendly languages, using iterator math to implement circular buffers of arbitrary data types. They are a little bit slower to use than straight arrays, but they provide a nice syntax for fixed sized buffers and are helpful in cases where you will be prepending and appending elements.
I am pretty certain that queues are implemented as circular buffers under the hood, so much of the infrastructure is already in place, this is mostly adding a new API. Added bonus: the explicit circular buffer can be synchronous, unlike the queue, so for example you can put them in subroutine VIs.
It should be easy to convert 1D arrays to/from circular buffers. Array->CB is basically free, the elements are in order in memory. CB->Array requires two block copies (most of the time). This can be strategically mananged, much like Reverse or Transpose operations.
Use cases:
You can implement most of the following two ideas naturally:
http://forums.ni.com/t5/LabVIEW-Idea-Exchange/Looping-Input-Tunnels/idi-p/2020406
http://forums.ni.com/t5/LabVIEW-Idea-Exchange/New-modes-on-auto-indexed-input-array-tunnels-in-loops...
Circular buffers would auto-index and cycle the elements and not participate in setting 'N'.
You can do 95+% of what I wanted to do with negative indexing:
http://forums.ni.com/t5/LabVIEW-Idea-Exchange/Negative-Values-in-Index-Array-or-Array-Subset/idi-p/9...
A lot of the classic divide and conquer algorithms become tractable in LV. You can already use queues to implement your own stack and outperform native recursion. A CB implementation of the stack would be amenable to subroutine priority and give a nice performance kick. I have done it by hand for a few datatypes and the beauty and simplicity of the recursive solution gets buried in the implementation of the stack. A drop-in node or two would give you a cleaner look and high-octane performance.
Finally, perhaps the most practical reason yet: simple XY Charts.
As for appearance I'd suggest a modified wire like the matrix data type. Most if not all Array primitives should probably accept the CB. A few new nodes are needed to get/set buffer size and number of elements and to do the conversions to/from 1D arrays. The control/indicator could have some superpowers: set the first element, wraparound scrolling (the first element should be highlighted).
