X-cellent.

(I know, my puns are getting worse. Sorry.)

Continuing my posts of rare-letter names, it is now time for X. X is the third-least-common starting letter in American names for both boys and girls, after U and Q. Chances are you can name Xavier and Xander for boys, but girls are more difficult--perhaps rare name-nerd favorite Xanthe springs to mind, or Spanish imports Xiomara and Ximena.
X-names may be hard to come by in English, but I bet we can find plenty abroad....
(if you're feeling a bit of deja vu, I did indeed do an X-themed post a few years ago, but this time I'm focusing solely on names starting with X ;) )

Boys:

• Xabier (shah-bee-ehr, Basque, Galician)--form of Xavier. Other forms include Xaver (KSAH-vehr, German).
• Xacobe (shah-KAW-bay, Galician)--form of Jacob
• Xanthus (KSAHN-toos, ZAN-thus, [ancient] Greek)--"yellow, blond". Other forms include Xanthias (ksahn-TEE-ahs, ZAN-thee-as).
• Xanti (shahn-tee, Basque)--form of Santiago
• Xenios (KSEN-ee-os, ZEN-ee-os, [ancient] Greek)--"hospitality".
• Xenophon (ZEN-ah-fon, ksen-ah-FOHN, [ancient] Greek)--"foreign voice"
• Xesús (shay-SOOS, Galician)--form of Jesus/Joshua. Other forms include Xosué (shaw-soo-AY).
• Xherdan (JEHR-dahn, Albanian)--poss. "necklace"
• Xhevahir (jev-ah-HEER, Albanian)--from Turkish, "jewel"
• Xhevdet (JEV-det, Albanian)--poss. from Arabic [via Turkish], "excellence"
• Xian (SHEE-ahn, Galician)--form of Julian
• Xicu (SHEE-koo, Asturian)--poss. a form of Francis/Francisco
• Ximeno (hee-MAY-noh, Spanish)--poss. a form of Simon
• Ximo (SHEE-moh, Catalan)--short form of Joaquín/Joaquim
• Ximun (shee-moon, Basque)--form of Simon
• Xoán (shoh-AHN, Galician)--form of John. Other forms include Xuan (SHOO-ahn, Asturian).
• Xulio (SHOO-lee-oh, Galician)--form of Julio/Julius
• Xunio (SHOO-nee-oh, Galician)--form of Junius
• Xurxo (SHOOR-shoh, Galician)--form of George
• Xustino (shoos-TEE-noh, Galician)--form of Justin

Girls:

• Xabierra (shah-bee-ehr-rah, Basque)--feminine of Xabier/Xavier. Other forms include Xaveria (ksah-VEHR-ee-ah, German), Xaverine (ksah-ver-REE-neh, German; zah-veh-REEN, French), Xaviera (zay-vee-EHR-ah, English; ksah-vee-EHR-ah, Dutch), and Xavière (zahv-YEHR, French), 
• Xana (SHAH-nah, Portuguese)--short form of Alexandra
• Xandra (KSAHN-drah, Dutch; SHAHN-drah, Galician; ZAN-drah, English)--short form of Alexandra
• Xanthe (KSAHN-tay, ZAN-thee, [ancient] Greek)--"yellow, blond". Other forms include Xanthis (KSAHN-tis, ZAN-this) and Xantho (KSAHN-toh, ZAN-thoh).
• Xanthippe (ksahn-TEE-pay, zan-THIP-ee, [ancient] Greek)--"yellow horse". Other forms include Xanthippi (ksahn-TIP-pee, Greek), and Xantippa (zan-TIP-pah, Latin).
• Xelha (SHEL-hah, Mayan)--"spring of water". Also spelled Xel-Ha.
• Xenia (ksen-EE-ah, Greek)--"hospitality". Other forms include Xene (KSEN-ee, Greek) and Xenie (ksen-EE-eh, Czech). 
• Xènia (SHEN-yah, Catalan)--short form of Eugenia. Portuguese form is Xenia (shen-EE-ah).
• Xenoveva (shen-aw-VEH-vah, Asturian, Galician)--form of Genevieve
• Xesca (SHES-kah, Catalan)--form of Francesca
• Xheneta (jen-EH-tah, Albanian)--poss. "paradise"
• Xhevahire (jev-ah-HEER-eh, Albanian)--from Turkish, "jewel"
• Xia (shee-AH, Mandarin)--"daybreak" or "summer" [also a surname]
• Xiana (shee-AH-nah, Galician)--feminine of Xian/Julian
• Ximena (hee-MAY-nah, Spanish)--feminine of Ximeno
• Xiomara (see-oh-MAHR-ah, Spanish)--poss. from Germanic, "famous battle"
• Xoana (shoh-AH-nah, Galician)--form of Joan/Jane
• Xochitl (SHOH-chee-tl, Nahuatl)--"flower"
• Xulia (SHOO-lee-ah, Asturian, Galician)--form of Julia
• Xunia (SHOO-nee-ah, Galician)--form of Junia

Unisex:

• Xiu (shee-oo, Mandarin)--"beautiful" [usually fem.], or "rest" or "build" [both masc.]
• Xuan (soo-un, Vietnamese)--"spring"
• Xue (shoo-eh, Mandarin)--"snow" or "learning"
• Xun (shoon, Mandarin)--"fast, sudden"