Gears of War 2 Cheats

Successfully complete the indicated task to unlock the corresponding skin in Multiplayer mode.

Accomplish the indicated achievement to get the corresponding number of Gamerscore points:
Green as Grass (10 points): Train the rook (any difficulty).
It's a Trap! (10 points): Story progression in Act 1, Chapter 2.
Escort Service (10 points): Story progression in Act 1, Chapter 4.
Girl About Town (10 points): Story progression in Act 1, Chapter 6.
That Sinking Feeling (10 points): Story progression in Act 2, Chapter 4.
Freebaird! (10 points): Story progression in Act 2, Chapter 5.
Heartbroken (10 points): Story progression in Act 2, Chapter 6.
Longitude and Attitude (10 points): Story progression in Act 3, Chapter 3.
Tanks for the Memories (10 points): Story progression in Act 3, Chapter 4.
Water Sports (10 points): Story progression in Act 3, Chapter 6.
There's a Time for Us (10 points): Story progression in Act 4, Chapter 2.
Better Wrapped in Beacon (10 points): Story progression in Act 4, Chapter 3.
Have Fun Storming the Castle (10 points): Story progression in Act 4, Chapter 6.
And the Horse You Rode in On (10 points): Story progression in Act 5, Chapter 1.
You Are the Support, Son (10 points): Story progression in Act 5, Chapter 2.
Brumak Rodeo (10 points): Story progression in Act 5, Chapter 4.
Does This Look Infected to You? (10 points): Story progression in Act 5, Chapter 5.
Tourist of Duty (25 points): Complete all campaign acts on Casual Difficulty.
Guerilla Tactician (50 points): Complete all campaign acts on Normal Difficulty.
Artist of War (75 points): Complete all campaign acts on Hardcore Difficulty.
Suicide Missionary (150 points): Complete all campaign acts on Insane Difficulty.
Collector (5 points): Recover 5 collectibles (any difficulty).
Pack Rat (15 points): Recover 20 collectibles (any difficulty).
Completionist (30 points): Recover all 41 collectibles (any difficulty).
One-Night Stand (10 points): Complete 1 chapter in co-op on any difficulty (Marcus or Dom).
Open Relationship (30 points): Complete 10 chapters in co-op on any difficulty (Marcus or Dom).
Friends with Benefits (50 points): Complete all acts in co-op on any difficulty (Marcus or Dom).
Once More, With Feeling (10 points): Perform 30 perfect active reloads (any mode).
Takes a Licking (30 points): Melee 30 Tickers (any mode).
Organ Grinder (10 points): Kill 30 enemies with a cover mounted Mulcher (any mode).
Shock and Awe (10 points): Kill 30 enemies with the heavy Mortar (any mode).
Said the Spider... 

To unlock the Insane Difficulty level, complete the game once through on any difficulty setting previously available

To unlock RAAM for use in multiplayer, have the “A Dish Best Served Cold” achievement on your hard drive from the original Gears of War.

To unlock Dizzy Wallin for use in multiplayer, complete Act 1 in single-player mode on any difficulty.

To unlock Lt. Minh Young Kim for use in multiplayer, have the “Time to Remember” achievement on your hard drive from the original Gears of War.

To unlock Tai Kaliso for use in multiplayer, complete Act 3 in single-player mode on any difficulty.