GG

GG or gg is an abbreviation for "good game":

Some people say "gg" (pronounced "jee jee") ironically over voice chat instead of "good game". This is similar to the ironically hip usage of other internet slang such as "LOL" (pronounced "lawl") or "heart" in actual speech.
 * Normal use: It is used very commonly at the end of GvG matches, Global Tournament matches or arena matches to indicate that the game has been fun.
 * Ironical use: Many players also use GG at the end of a especially bad match.
 * Instead of end: Since GG is used at the end of matches, it is sometimes used to indicate the end. For example, a player might type GG after a monk left during a hard mission to indicate that the party is no longer able to finish the mission.
 * The Zaishen in the Zaishen challenge say "gg" after beating ateam, much to the annoyance of their human apponants :)