One of the most natural adoptees to professional wrestling in New Japan history, Masakatsu Funaki eschewed being one of the best Japanese pro wrestlers to become a pioneer in Mixed Martial Arts.  Funaki would leave New Japan and later co-found Pancrase with Minoru Suzuki wherein the late 90's he was considered one of the greatest fighters in the world.  After a loss to Rickson Gracie in 2000, he retired from fighting but would come back and later return to pro wrestling after a long absence, and he became the All-Japan Triple Crown Heavyweight Champion.  In terms of MMA influence few are in his league but translating that to a WWE Hall of Fame induction is a hard sell.