Xavier (Pronounce Zavier), Xeno (Pronounce Zeno) and Xander (Pronounce Zander). There would be more but these are the only ones at the top of my head.
An actor whose first name starts with X is Xavier Samuel, who played Riley in the Twilight Saga. Other actors include Xavier Dolan and Xavier Fagnon.
A type of small bird, "xenops" is pronounced "zenn-ops".
Xavier Cugat... though Xavier wasn't actually his first name per se. (He's also dead now.)
Bel Xavier's birth name is Isabel Xavier.
20,044 people have the first name of Xavier.
Xavier Manteiga's birth name is Xavier Manteiga Pousa.
Xavier Ruano's birth name is Xavier Ruano Perales.
Xavier Rivers's birth name is Xavier Arco Rivers.
Xavier Berraondo's birth name is Xavier Berraondo Cavall.
Xavier Atencio's birth name is Francis Xavier Atencio.
Xavier Bosch's birth name is Xavier Bosch i Sancho.