Padma Sambhava, or Guru Rinpoche, is the all-around culture hero of Tibet, coming from the south in the 8th century. He is famous for the introduction of tantric teachings which later became the foundation of the Nyingma school of Tibetan Buddhism. Many stories are told of his overcoming the opposition of the native shamanistic Bon religion, and at the end of his life, took his leave of his disciples and walked off into the mountains never to be seen again.
The first video is so quirky I had to include it. The second has great visual representations of Guru Rinpoche. The third has his 7 line supplication in Tibetan. In English it goes like this:
In the northwest of the land of Uddiyana
On a blooming lotus flower
You have attained supreme, wondrous siddhi
You are renowned as Padmakara
Surrounded by your retinue of many dakinis
We practice following your example
Please approach and grant your blessing
Guru Padma Siddhi Hum
The mantra that many Western Buddhists learn is: Om Ah Hum Vajra Guru Padma Siddhi Hum, sometimes followed by Vajra Samaja Siddhi Phalam Hum Phat! With a gesture of the hands folded together chest high, facing forward and shooting outwards on Phat! An alternative is a snap of the fingers. Or so I learned from one devotee.