Liquid Metal Green Weapons – Free promotion, not currently announced Liquid Metal Black Weapons – Included with the Gears of War 3 Season Pass
Infected Omen Weapons – Included with the Gears of War 3 Epic Edition, Limited Edition Console, or Limited Edition Controller Golden Omen Weapons – Reach Level 100 in Gears of War 3 Skin Sets for Multiple Weapons (most of these are for the first five weapons)
Here is the list of weapon skins you can unlock, and what must be done to unlock them. Some of these are retroactive from the previous games, and should unlock automatically if you met the criteria from that game. In Gears of War 3 for the Xbox 360, there are a lot of weapon skins you can unlock by performing certain tasks.
