Rokushiki

Rokushiki (六式 Rokushiki?, literally meaning "Six Styles") is a special, superhuman martial arts style. In the Viz Manga and FUNimation dub, they are called the Six Powers.

Overview
The strength of a Rokushiki user is measured by Doriki, which some people can use "Te-awase" to calculate with. The higher the level, the stronger each technique's potency becomes. Most of the users have their own variation of each technique, to increase their versatility and originality. Also, certain users tend to be more specialized in one technique.

Rokushiki is the main style of combat for the World Governments's secret CP9 agents, but some  Marines have also demonstrated its usage. It is unknown exactly how much Rokushiki is spread around the Marines.

Trivia

 * The only mainstream Rokushiki technique not used in Hedgehog Piece so far has been Kami-e.
 * Ironically, Rokushiki has been introduced not by the CP9 but rather by the select Marines that have somehow obtained knowledge on how to use it.
 * It would appear Rokushiki is a lot more well known than expected, since people like Johnny and Drago Kai know some techniques without being Marines.
 * It's also interesting that they'd both only been shown knowing Soru, which is sometimes regarded as the "gateway" Rokushiki technique.