YouTube averaged an astounding 4 billion views per month during 2012, and its YouTube Rewind for 2012 lists the top ten videos that contributed to those numbers. According to the site, viewers "participated in conversations at a global scale, uploading videos to share ideas on everything from nonprofit campaigns, to political satire, to new and surprising voices and talents." And the videos we watched the most were just as varied, ranging from parenting in the social media age to a lip dub of the Carly Rae Jepsen hit "Call Me Maybe," featuring Justin Bieber and Selena Gomez. But the heavyweight champ of 2012 was PSY's "Gangnam Style," which amassed nearly 1 billion views in just 6 months, eventually making it the most watched YouTube video ever. PSY himself makes an appearance in a mashup that celebrates the "culturally defining moments of 2012." Check it out below, along with the top 10 trending YouTube videos of 2012.