Hi, this is my first post and i didn't know where to put this as there seems to be no thread for COD: Online.
Here are a couple Gamertag addresses that i found.
For the last two, you need to set them in pregame lobby, then wait till the game ends and it should change values.
0C1A5CC8 - pregame name
0C1A5D28 - Client 1 pregame name
0C1A3CE8 - Client 2 pregame name