Slowing making progress towards this achievement. I've only done a bit of boosting game modes, everything else I've done online. I've nearly done all the rifles, and most other random ones. The game modes seem to be taking me ages though. Hope to have it unlocked by half way through next year.
Gears of War Veteran
Seriously - unlocked 6/6/07
Seriously 2.0- unlocked 2/2/10
Seriously 3.0- unlocked 21/3/13
Total Online Kills - 150,000+