I have written a similar answer before, so I'm posting that content.
Before knowing the powerful mantras, let us first understand what are mantras, how they came into existence, when to chant and what is the use of chanting.
Mantras are like medicine for the soul, they are the best way to connect to God.
- Mantras, Ashtothram, Stothrams, Sahasranamam all are for praising the Almighty where in you explore the inner meanings and thus realize the greatness of God and strive to merge into Him by attaining the ultimate bliss.
- Our ancestors while performing Yagnas or doing Tapasya, used to chant various hymns / mantras, to please God and get their various wishes fulfilled.
- You have to believe in the mantra and Stothrams and pronounce them perfectly with pure love, trust and belief then, you can feel them in your chitt ( soul ), then the mantras does wonders to you.
What is a mantra ?
- Mantra is a word / sound, which is repeated to help in concentration while meditating. When ever you recite any mantra, you can feel the positive vibes / energy.
- Every mantra has amazing power and strength. Foremost, have trust and belief in the mantra or Stotram. Mantras has favorable outcome and help in erasing obstacles. You start to progress spiritually by chanting mantras, You will be in the path of Enlightenment / realization.
- Mantras help in washing away of your sins and helps in purification of speech. You would start living according to Dharma and for sure , you will stop using filthy language.
- If you are not able to chant any mantra, then you can chant any God's name.
According to Sama-Veda, it is believed that, chanting of mantras will activate your Chakras and thus lead you into path of Enlightenment, and even the people who listen to Mantras had noticed increased temperatures around the Chakras.
Few mantras which you can chant are ::
- Shiva :: you would observe that after chanting Shiva for few times, it would transform into Vashi, means Shiva would take over you, that is Vashikaran
- Shivoham = Shiva + aham ( I ), this means you are Shiva, that is why the mantra is, Chidananda roopah shivoham shivoham, which means the blissfulstate of me ( soul ) is Shiva.
- When you chant the Maha mrityunjaya mantra, you would have a long and peaceful life ( death conquering mantra ).
- When you chant Om, you can feel the cosmic Energy.
- Chant the Panchakshari mantra “ Namah Shivaaya “, and you can feel the positive vibes, and you will realize that your body is made up of the five elements of the nature and everything is Shiva.
- Om Namo Narayanaya, chant this mantra for Lord Vishnu, the protector and operator for your life and even the entire Universe.
Great devotees of Shiva namely Bhaktha Markendeya and Sati Savitri, who could overcome their Karma, because of chanting the Maha mrityunjaya mantra, and Panchakshari mantra “ Namah Shivaaya” have set examples for us.
Even a dacoit like Valmiki, transformed into a great poet by chanting Rama’s name and wrote “Ramayana” ( he could not pronounce the word “Rama” and pronounced it as “Mara”.)
Goddess Parvathi, did years of penance and chanted Shiva's name and thus got God Shiva as her husband.
King Ravana was able to get Darshan of Shiva and could even lift the Khailash mountain by chanting Shiva's name and mantra.