KIWIZ RULE THE WORLD!
Its just that nobody knows it yet...
He ain't as high as me.
~v~
But in all seriousness, his rank, by the end of Halo 3, is Master Chief Petty Officer of the Navy, highest enlisted rank.
The highest ranking SPARTAN is still held by Fred-104, though, and all time it was Carter-259 until his supposed death.
In other words hes the highest fighting rank?