X can refer to:
  • The X-Universe series, a long-running series of wide open sandbox games.
  • X, a punk band.
  • X/1999, a manga series referred to as X in Japan.note 
  • X, a comic book series by Dark Horse Comics.

Tropes brought to you by the letter X:

See This Trope Is X for tropes in which "X" is a placeholder.

You may also have been looking for the Turn-Based Tactics series XCOM.