People:
* Xander (a popular male name)
* Xenia (a Greek name meaning "hospitality")
* Xavier (a name of Spanish origin)
* Xerxes (a historical Persian king)
* Xochitl (a Mexican name meaning "flower")
* Xana (a name of Greek origin)
* Xiomara (a name of Hispanic origin)
* Ximena (a Spanish name)
* Xi Jinping (current President of China)
Other:
* X-Men (a popular comic book series and film franchise)
* Xbox (a popular video game console)
* X-ray (a type of electromagnetic radiation)
* X Factor (a popular talent show)
* X marks the spot (a phrase associated with treasure hunting)
Let me know if you'd like more examples!