Source: videogamesblogger.com

This Gears of War 2 guide will show you all available codes, cheats and help with unlocking modes, maps & skins, and get achievement points of the Xbox 360-exclusive third-person shooter game. Time to show those Locust who’s boss!

Let’s start with unlocking an additional difficulty setting for the main campaign: when you’ve finished the game once on any difficulty level, you unlock the Insane difficulty mode.

Did you know your copy of Gears of War 2 comes with a code for the free Flashback Map Pack? Yes, it does. Check on the inside, behind the Gears of War 2 manual on a separate piece of paper you’ll find a scratch card with a code that unlocks five maps. Those five favorite multiplayer maps from the original Gears of War have been updated and made available to download and play in Gears of War 2. To download the Flashback Map Pack you’ll first off obviously need an Xbox Live Silver or Gold membership, and be signed in to Xbox Live from the Xbox 360 Dashboard. From there you select Xbox Live Marketplace, then select Redeem Code when prompted, enter your code, and your download will be waiting for you. — On the same scratch card is a claim code that gives you 48 hours of Xbox Live Gold membership, so you can try out the online multiplayer modes in Gears of War 2 for free.

If you buy the Gears of War 2 Limited Edition, it comes with an exclusive Xbox Live code that you can use once to unlock a gold-plated Lancer Assault Rifle for in-game online play. Enter the code the same way you did the (above mentioned) Flashback Map Pack code. After the download is complete, the Golden Lancer becomes available in all multiplayer modes including Horde and Training.

To unlock new skins for in multiplayer, you must complete the following tasks…
* Anthony Carmine: Successfully complete Act 1 in the original Gears Of War (have any Act 1 achievement unlocked from that game).
* Dizzy Wallin: Successfully complete Act 1 in Single Player mode.
* Flame Grenadier: Successfully complete Act 4 in Single Player mode.
* Kantus: Successfully complete Act 2 in Single Player mode.
* Lt. Minh Young Kim: Find 10 COG tags in the original Gears Of War (have the “Time To Remember” achievement unlocked from that game).
* RAAM: Defeat RAAM in the original Gears Of War (have the “A Dish Best Served Cold” achievement unlocked from that game).
* Skorge: Successfully complete Act 5 in Single Player mode.
* Tai Kaliso: Successfully complete Act 3 in Single Player mode.

You can unlock 50 Achievements in the game to get a total of 1,000 Gamerscore points. Here’s the full list of them all…

Achievement (Gamerscore points) — How to unlock it.
1. Green as Grass (10) — Train the rook (any difficulty).
2. It’s a Trap! (10) — Story progression in Act 1, Chapter 2.
3. Escort Service (10) — Story progression in Act 1, Chapter 4.
4. Girl About Town (10) — Story progression in Act 1, Chapter 6.
5. That Sinking Feeling (10) — Story progression in Act 2, Chapter 4.
6. Free Baird! (10) — Story progression in Act 2, Chapter 5.
7. Heartbroken (10) — Story progression in Act 2, Chapter 6.
8. Longitude and Attitude (10) — Story progression in Act 3, Chapter 3.
9. Tanks for the Memories (10) — Story progression in Act 3, Chapter 4.
10. Water Sports (10) — Story progression in Act 3, Chapter 6.
11. There’s a Time for Us (10) — Story progression in Act 4, Chapter 2.
12. Better Wrapped in Beacon (10) — Story progression in Act 4, Chapter 3.
13. Have Fun Storming the Castle (10) — Story progression in Act 4, Chapter 6.
14. And the Horse You Rode in On (10) — Story progression in Act 5, Chapter 1.
15. You Are the Support, Son (10) — Story progression in Act 5, Chapter 2.
16. Brumak Rodeo (10) — Story progression in Act 5, Chapter 4.
17. Does This Look Infected to You? (10) — Story progression in Act 5, Chapter 5.
18. Tourist of Duty (25) — Complete all campaign acts on Casual Difficulty.
19. Guerilla Tactician (50) — Complete all campaign acts on Normal Difficulty.
20. Artist of War (75) — Complete all campaign acts on Hardcore Difficulty.
21. Suicide Missionary (150) — Complete all campaign acts on Insane Difficulty.
22. Collector (5) — Recover 5 collectibles (any difficulty).
23. Pack Rat (15) — Recover 20 collectibles (any difficulty).
24. Completionist (30) — Recover all 41 collectibles (any difficulty).
25. One-Night Stand (10) — Complete 1 chapter in co-op on any difficulty (Marcus or Dom).
26. Open Relationship (30) — Complete 10 chapters in co-op on any difficulty (Marcus or Dom).
27. Friends with Benefits (50) — Complete all acts in co-op on any difficulty (Marcus or Dom).
28. Once More, With Feeling (10) — Perform 30 perfect active reloads (any mode).
29. Takes a Licking (30) — Melee 30 Tickers (any mode).
30. Organ Grinder (10) — Kill 30 enemies with a cover mounted Mulcher (any mode).
31. Shock and Awe (10) — Kill 30 enemies with the heavy Mortar (any mode).
32. Said the Spider to the Fly (10) — Kill 10 enemies with a planted grenade (any mode).
33. Crowd Control (10) — Melee 10 enemies down with the Boomshield equipped (any mode).
34. Smells Like Victory (10) — Kill 30 enemies with the Scorcher Flamethrower (any mode).
35. Variety Is the Spice of Death (30) — Kill an enemy with every weapon in the game (any mode).
36. Seriously 2.0 (50) — Kill 100,000 enemies (any mode).
37. Standing Here, Beside Myself (10) — Win 3 matches of Wingman (public).
38. Beat the Meatflag (10) — Capture 10 meatflags in Submission (public).
39. It’s Good to be the King (10) — Win 10 rounds of Guardian as the leader (public).
40. You Go Ahead, I’ll Be Fine (10) — Win three matches of King of the Hill (public).
41. Back to Basic (10) — Successfully complete the 5 lessons of multiplayer Training Grounds.
42. Party Like It’s 1999 (30) — Play 1999 rounds of multiplayer (any mode).
43. Around the World, Again (30) — Win a multiplayer match on each map (any mode).
44. Dirty, Dirty Horde (20) — Survive the first 10 waves of Horde (any difficulty, any map).
45. Hoard the Horde (30) — Survive all 50 waves of Horde (any difficulty, any map).
46. Crossed Swords (10) — Win 10 chainsaw duels (any mode).
47. A Parting Gift (20) — Kill 10 enemies with a grenade while down but not out (any mode).
48. Pound of Flesh (10) — Use a meatshield to save your life 10 times (any mode).
49. Photojournalist (10) — Submit a spectator photo.
50. Kick ‘Em When They’re Down (10) — Perform all 11 unique executions on a downed enemy.

Big thanks to Mike and the folks at Mycheats & Cheatcc.