FTW: For The Win
An enthusiastic emphasis to the end of a comment, message, or post. Sometimes genuine, but often sarcastic.
Originated from the game show Hollywood Squares where the result of the player’s response is expected to win the game.
[source: Urban Dictionary: ftw]
[editor’s comment: my minorly dyslexic mind connects this with WTF, so I always hear “f**k the what?” in my head when I see FTW.]