Y Not

Xtreme Kool Letterz demands that certain letters are used. X and Z are generally considered the coolest of them all, which can lead to people forgetting all about the poor overlooked middle child: Y.

Y is Y forgotten? Maybe it's a case of lost/mistaken/confused or dual (consonant or vowel) identity. Maybe it's a case of All the other Letters. But one thing is for sure: people don't like Y.

Examples of Y Not include:

In Mega Man X, they have X and Zero (possibly for reasons related to the Japanese symbols for "right" and "wrong").
Powerpuff Girls gives an upgrade to Chemical X...Chemical Z!
Pringer X gets upgraded straight to Pringer Z, too. I can't think of a conspicuous missing W that doesn't involve conspicuous missing A through V as well. Y is the more prominent missing link.
This funny Flash animation: Sometimes Y
Possibly spoofed in a Family Guy episode where Stewie states that he hates someone "like the vowels hate Y!" Cue cut-away gag where the letter Y shows up late to a board meeting with the letters A, I, O, U and E, obnoxiously chatting to the consonants on his cellphone.
There's Gundam X and Zeta Gundam (And Gundam ZZ), but no Gundam Y.
Averted in Yu-Gi-Oh! with Y-Dragon Head, part of XYZ-Dragon Cannon and its upgraded form VWXYZ-Dragon Catapult Cannon.
The Lithuanian alphabet is a real life example: unlike most languages, where Y is a second-to-last letter, here Y is tucked somewhere in the middle.