| If you ever find yourself within chatrooms in the transvestite, transsexual or transgender area of the internet then the abbreviation 'GG' takes on a different meaning, that being Genetic Girl. Or Genuine Girl, if you prefer - both mean the same thing. This usually means that the person using it was either born female or has merely tacked the letters 'GG' to the end of their name to pretend.
In gaming terms, as a result of my extended liason with Yahoo! Pool, 'GG' seems to have lost its meaning due to overuse*. Instead of meaning, "Hey, that was a damn good game and I thoroughly enjoyed it. Thanks", it's become some standard quick line to stick at the end of any online multiplayer game.
The T*Girl Team Fortress League regularly collapse into fits of confusion over this abbreviation's unfortunate double meaning.
* see also: lol. speaking personally, i can't seem to help reading that one with a deadpan tone of voice. | 
