One of the newer short forms of Alexander, Xander is a spelling that first saw the spotlight via Buffy the Vampire Slayer, and then as Vin Diesel's character in XXX. This relative newcomer, along with phonetic spelling Zander, is now just outside the Top 200 names in the USA. Mad Men star January Jones named her son Xander Dane.
Even shorter forms Xan and Zan are now also being used on their own. Xan is a character in the P. D. James novel The Children of Men, and is a favorite choice of computer game creators.