What is a Bible verse that starts with the letter "X"?

It may depend on your version of the Bible.

According to the search of University of Michigan's electronic version of the King James Bible (and confirmed with Biola's Bible Unbound), the only WORDS (let alone verses) of that version of the Bible beginning with the letter X are three instances of "Xanthicus" (a month) in the apocryphal second book of Maccabees, and none of them begin a verse.

Conversely, some modern translations DO have such verses. For example, the "Contemporary English Version" (as searched through Bible Gateway) has as its Esther 2:17 :
"Xerxes liked Esther more than he did any of the other young women. None of them pleased him as much as she did, and right away he fell in love with her and crowned her queen in place of Vashti."

Xerxes was named Ahasuerus in the King James version, so doesn't begin any verses there. I guess my answer is that you've given an ill-formed question without naming which translation you're using.

In the King James version...
There does not appear to be a verse starting with the letter x. As far as I am aware, there is only one word beginning with an X. The name, Xerxes, in the book of Esther!

http://wiki.answers.com/Q/What_is_a_bible_verse_starting_with_the_letter_X

I was looking for a translation that would have "Xerxes" starting a verse in Esther. You found it, Kevin. Here's the link:

http://www.biblegateway.com/passage/?search=Esther%202:17&version=CEV

There is confusion as to whether this is Xerxes the Great or Artaxerxes I or II.

https://en.wikipedia.org/wiki/Ahasuerus#In_the_Bible