The 16 Secret or "Hidden" fists are

Kikaku Ken
Shuki Ken
Fudo Ken
Kiten Ken ( Shuto )
Shi Shin Ken
Shitan Ken
Shako Ken
Shito Ken ( Boshi Ken )
Shikan Ken
Koppo Ken
Happa Ken
Sokuyaku Ken
Sokki Ken
Sokugyaku Ken
Tai Ken
Ki Ken