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.
FTL (For The Lose):
The opposite of for the win. Used to describe a situation or thing that is undesirable, whether that situation was caused by the speaker or by someone else. Often shouted when someone is killed in a multiplayer game. Most commonly used by gamers, though it's gaining popularity in general online culture for anything that's disliked.
Both of these combinations of letters would totally make my Top 5 Favorite Acronyms list. I find them hilarious, and often perfect as a way of getting my point across.
Also, as a gamer who spent 2 years playing FFXI Online, and 3 playing WoW, "ftw" and "ftl" are pretty much the best tri-letter terms anyone could ever use, ever. The only one that even comes close is "lul", a complete mockery of the over-used "lol", and that seems so rarely used by any other than yours truly.
Any term that can be used in a humorous way, with OR without sarcasm, is immediately listed as Gold in my book. For instance, in this picture I drew of Link from the Legend of Zelda-
"ftw" can be interpreted however you may wish. One who is a fan of the Zelda series might think, "OMG IT'S LINK HE'S TOTALLY FTW", whereas one who couldn't tell the difference between the Triforce and a fucking falafel might think, "WTF IS THAT, HAHA HE'S SAD SO HE'S LIEK DEFINITELY SAYING FTL, NOT FTW. IRONY IS SO COOL RIGHT NOW. SO IS MISUSING THE TERM IRONY." So you see, in nearly any situation involving the term, everyone wins.
In conclusion, the acronyms "ftw" and "ftl" are both "for the win".
Oh yeah, and here's an owl. Too bad he doesn't give a hoot about acronyms.