Eight ways to pronounce the letter X, from wordplay maven Dmitri Borgmann:

eks: x-ray
gz: exist
gzh: luxurious
kris: Xmas
ks: sex
ksh: anxious
z: xylophone
__: faux pas

He adds three more: According to Webster’s Second Edition, xeres is an alternate name for sherry wine in which the X can be pronounced either as H or as SH. And arguably the X in except is pronounced like the letter K, as “the sibilant portion of the usual X sound has fused with the sound of the C immediately following.” If we accept these, then the total rises to 11.

(Dmitri A. Borgmann, “The Ultimate Homonym Group,” Word Ways 17:4 [November 1984], 224-228.)