2011 was an incredible year for social media, especially the 140-character blog, Twitter. With one tweet, breaking news spread, lives were changed and pop-culture was changed forever.

First up, who could forget Charlie Sheen's bizarre catchphrases? They quickly became popular hash tags and part of our vocabulary.

Then there's that late Sunday night news in May that the world's most wanted man had been killed. The news of Osama bin Laden's death spread with a tweet from the chief of staff for the office of Donald Rumsfeld.

What about using social media for good? The fast food chain Wendy's used a promoted tweet to raise $50,000 for foster children.

Lastly, even the pope jumped on the social media train. He sent his first tweet using an iPad this past summer.

Click here to see more of Mashable.com's most memorable tweets of 2011.