(Code can be found in Scripts)
This simple tool came about when a member of my team needed to mirror a mesh from its pivot after he had UV'd it, essentially cutting his work in half on many of his props. The old way he would have done this was by duplicating the mesh and repositioning it to where he needed but just trying to match it by eye. With this tool it does it much more accurately and much faster (at the click of a single button!).
This tool gives the option to Mirror On Pivot via x,y, or z axis.