QQ is an acronym often used in online communication to signify two crying eyes. It is usually used in the pejorative such as "QQ more nub" meaning "Cry more, newbie."
"QQ" has become a popular term, and can also be used to reply to a poster that the person thinks is whining. It is generally seen as trolling if the post only consists of QQ, for example:
Hunter: Why do hunters always get nerfed?
Within the context of World of Warcraft one will often see "less QQ more pewpew", meaning basically "try crying less and fighting back more", for example:
Player A: Why do level 70s always gank? What's the point?
Reply: Less QQ more pewpew.
This term came from the Warcraft series. The quick way to exit out of the game and enter back into the chat lobby was to press alt then Q twice, hence QQ. It also vaguely resembles an emote of crying eyes.
It became a way of insulting noobs and telling them to get out or leave the game.