Padmasambhava: This mantra serves to
protect us from negative forces of a
spiritual or physical nature and to
achieve the qualities and virtues needed
to support us on the path of spiritual
development.

Mantra of Padmasambhava
Tibetan Pronunciation

Om ah hum
vajra guru padma siddhi
hum

http://www.youtube.com/watch?v=qmNtizr5kA8

About the vajra guru mantra

Padmasambhava