The Great Compassion Mantra 大悲咒

This is the most widely read mantra in Taiwan (with the possible exception of the much shorter Tibetan mantra, Om mani padme hum 唵嘛呢叭咪吽 ॐ मणि पद्मे हूँ).

The entire mantra is read in Chinese characters using Mandarin (maybe Taiwanese or Hakka in a fwe cases), even though it makes *no sense* since the whole thing is just a transliteration of Sanskrit.

For example, the opening line part of the sutra reads:
南無．阿唎耶．婆盧羯帝．爍缽囉耶
na-mo wo-li-ye po-lu-jie-di-shuo-bo-la-ye

Which comes from sanskrit:
Nama āryāvalokite-śvarāya

Meaning "Adoration to the noble (ārya) Lord (īśvarā) who looks down (avalokite)." (皈依三寶皈依聖觀自在).

You can get more information in Chinese here, and more in English here.