There were several guitarists who made important contributions, some names from the early days are Javier Molina, Niño Ricardo and Ramón Montoya.
In 1930 one gifted guitarist, who had refined some techniques from classical guitar incorporated in flamenco by some of his predecessors, decided to record an album. The record companies in Spain didn't think there would be any interest, a company in Paris did, and the first flamenco-guitar album was a fact. In general, the availability of recordings (flamenco and others) had a significant impact on the development of flamenco.
The name of the guitarist is Sabicas. He worked with the famous female dancer Carmen Amaya, and many of today's great flamenco guitarists took lessons from him. He contributed to a movement towards a higher standard of perfection, that is continuing today. Perfection has always been important in flamenco. Implementing embellishments at the often high tempo without doing it (almost) perfect is considered pointless: it becomes kitsch. But Sabicas lifted it to the level of internationally recognized musical forms like jazz and classical music.

One of the great guitarists of today is Paco de Lucía. He is probably the most widely known flamenco guitarist, mostly due to his exercises in jazz. He is sometimes mistaken for a jazz guitarist, but he is flamenco through and through. He is just extremely gifted, and needs a challenge. He is probably the most important innovator in the recent history of flamenco. His genius, technical perfection and creativity not only made their mark on flamenco guitar: he met a singer that he connected particularly well to, and they formed an historical musical cooperation, adding an intensity to flamenco that was never heard before.

 His name is José Monje Cruz, better know as 'El Camarón de la Isla', or just Camarón. His death in 1992 shocked Spain to the same extend that the death of a famous torero would have, he was was a folk hero, the king of flamenco. He did for flamenco singing what Paco de Lucía did for flamenco guitar.
Camarón, like most flamenco artists, worked not just with one person: another guitarist of interest is 'Tomatito'. Of the almost 20 albums Camarón made, the first few were exclusively accompanied by de Lucía, later ones by Tomatito and some by both. Tomatito is one of the new generation of flamenco artists, the generation of 'flamenco joven' (young flamenco), a movement set in motion by Paco de Lucía. This shows how much alive flamenco is today: amongst this generation are as many high quality singers, dancers and guitarists as ever.

 Another great guitarist of 'flamenco joven' is Vicente Amigo. The flamenco magazine aficionao featured an interview with him. (photo taken in 'Muziekcentrum Vredenburg' in Utrecht, The Netherlands, by Liesbeth Ruysink.