The mantra I feel most called to chant in the past few years is the Ayur Mantra, a Veda chant from the Taittirīya āranyaka, an ancient text on ritual practices and spiritual philosophy.
Ayur is Sanskrit and the word means, essentially, Life. Ayur is Life, and the Ayur Mantra is a mantra that makes lifeforce flow like a pure and healthy river within, so I love to share it with students.
I learned this mantra initially from my Vinyasa krama teacher, Khushi Malhotra, who teaches this mantra along with the nyasa, the beautiful hand gestures/mudras that may accompany the mantra, and bring it deeper meaning and power somatically.
I have since learned the traditional way that the mantra is chanted (that is, according to traditional Veda chanting rules) from my teacher, Shantalah Sriramaiah.
You can watch a video and listen to the Ayur Mantra being chanted by Shantala and her students here.