JKD & KALI
The art of Jeet Kune Do (JKD) was developed by Bruce Lee. His aim was to develop a modern approach and get away from what he termed the "classical mess" of traditional martial arts.
Initially, termed Jun Fan Gung Fu, it was a development from his original style of Wing Chun. However, fighting with the larger Americans forced him to re-evaluate his art and he went on to develop JKD.
JKD has a conceptual approach: the art of combat through principles, not techniques. This made his art more adaptable.
From these core principles, he could develop a thousand techniques. In many ways it was a forerunner of modern MMA.