There is no official Marine Corps kilt uniform. Any you may have seen were either off-dauty Marine pipers (or some such) or the Marine Pipe and Drum Corps which is made up of former Marines. There is a move to create an official piper MOS in the Corps, but as far as I know it hasn't gone anywhere yet. (See the article about that here: http://www.military.com/forums/0,15240,82507,00.html)

There was a Marine pipe band in Ireland during WW II, but I don't think it was actually "official" in that the Corps never created an MOS or billets for it.

I think that there is some official recognition from other branches as far as special bands or parade units, but I am unsure about that. I do know that the Naval Academy has a pipe and drum corps (http://www.usna.edu/Pipes/ ), but that's about the extent of my knowledge beyond the military (i.e., the USMC).