Business Insider (via Valleywag) has a list of the 21 most used/obnoxious abbreviations used on Twitter. Let's see, they've got RT (Retweet), HT (hat tip), IRL (in real life), FML (fuck my life) and QOTD (quote of the day), just to name a few. Also, what?! OMG, they forgot OMG (oh my God). Whatev.