X-Ray
The only other word in the english language even worth mentioning that begins with the letter "X", besides xylophone. "X" is truly the gayest of the letters.
Example:
Teacher: Hey kids! What word begins with the letter "X"?
Kids: What the fuck do you think, moron? Fucking X-Ray and Xylophone, bitch!
Teacher: Hey kids! What word begins with the letter "X"?
Kids: What the fuck do you think, moron? Fucking X-Ray and Xylophone, bitch!