Originating on starcraft to be a legitamit way to end a game, win or lose. With the release of Warcraft III eventually it became a way to taunt the losing team. Many people use the phrase today in and out of Warcraft. Good Game Losers, the best clan on Azeroth, as well as after arguments people who have "won" the argument would say GG No Re(ply) KThx(Sarcastically And Blindly assuming you wont talk back) BBQ (No Idea Why).
Me: Good God You Suck, Get That Noob Shit Out Of Here
Noob: Shut Up!!!11one
Me: Good Game NoRe KThx