This Thread took me a while
I will also like to thank Nookie for letting me repost 
*Means its On Horizon Game Adder
*Means its not on Horizon game adder
A [details=Open Me] After Burner Climax*
After Burner T-Shirt – Unlock every EX option
Gold Flight Helmet – Obtain one of every medal type in Score Attack
Alan Wake*
Jacket and Scarf – Play the Limited Collector’s Edition Bonus disc
Alien Breed 2*
Barne’s Helmet – Kill 50 aliens
Body Armor – Complete single player
New
Alien Breed 3: Descent
Helmet – Launch Project X.
Space Suit – On Elite difficulty, finish Space Walk
Ancients of Ooga*
Fireling’s Mask – Complete all of the levels and revive the ancient
Healer’s Mask – Complete the trials
Aqua*
Commander’s Hat – Finish the campaign
Emperean Uniform – Finish the prologue
A World of Keflings*
Dragon – Make friends with the baby dragon release from the egg in theice
Helmet – Talk to the chief at the great hall in the ice kingdom [/details]
B [details=Open Me]Blur*
Friend Re-Challenge T-Shirt – Beat a friend’s re-challenge
Legend T-Shirt – Earn the Legend rank in multiplayer
Showdown T-Shirt – Beat every boss
Sticker T-Shirt – Unlock every achievement
Wreck T-Shirt – Wreck another car[/details]
C [details=Open Me]Comic Jumper*
Captain Smiley Hat – Finish the game
Star/Gerda T-Shirt – Finish the first level
Costume Quest*
Pumpkin Mask – Complete the game
Pumpkin Pail – Start a new game
Crackdown 2*
Freaky Slippers – Survive Agent Diagnostics and be deployed in Pacific City
Level 1 Agent Suit – Detonate every beacon
Official Agency Hoodie – Complete one of every objective type
Orb Shirt – Earn the First Blood achievement from Crackdown 1 then play Crackdown 2
Ruffian Hat – Detonate ever beacon in Hope Springs
PvP Agent Armor – Complete 15 minutes of Main (requires Deluge add-on)
PvP Agent Suit – Purchase Deluge add-on
Xbox Green Suit – Earn the Rocketeer achievement (requires Toy Box DLC)
Xbox Helmet – Earn the Rocketeer achievement (requires Toy Box DLC)
New
Crazy Taxi
Crazy Taxi T-Shirt – Play the game for five hours
Hawaiian Shirt/Leopard Print Tank Top – Play the game for 10 hours [/details]
D [details=Open Me]Dance Paradise*
King/Queen of Dance Hat – In Career mode, complete all level 3 songs
King/Queen of Dance Shirt – In Career mode, complete all level 6 songs
King/Queen of Dance Shoes/Boots – In Career mode, complete all level 4 songs
King/Queen of Dance T-Shirt/Top – In Career mode, complete all level 5 songs
King/Queen of Dance Shades – In Career mode, complete all level 2 songs
Darwinia+*
Red Darwinia T-Shirt – Win a game of Multiwinia on Xbox Live
Squad T-Shirt – Complete the Epilogue
Deadliest Warrior*
Samurai Armor – Complete Arcade mode on any difficulty setting
Samurai Helmet – Complete Arcade mode with every character on Deadliest difficulty setting
[b]Dead to Rights: Retribution*
GAC Armor – Complete the game on Officer difficulty or higher
GAC Helmet – In one level, get 30 headshots on Officer difficulty or higher
GCPD T-Shirt – Finish a level without firing one shot
Jack and Shadow T-Shirt – Achieve 20 Jack and Shadow kills on any level
Retribution T-Shirt – In the first mission, protect all of the hostages
DeathSpank*
Dragon Hatchling – Complete Ms. Heybenstance’s quest to save her dragon
Unicorn Poop T-Shirt – Kill the twin dragons guarding the artifact
DeathSpank: Thongs of Virtue*
DeathSpank Libre T-Shirt – Obtain the Obque guards’ secret password
Gingerbread Avatar Pet – Defeat the Ultimate Cookie in the Jungle zone
Deca Sports Freedom*
Deca Sports Freedom Special Wear – Achieve a 20-hit rally
Deca Sports T-Shirt – Enter sudden death in any game
Hashiskue T-Shirt – Say “Hudson” into the Kinect microphone in the Locker Room
Destination: Arcade*
Dragon Pet – Find the dragon in the arcade
Hoodie – Check out Destination: Arcade
Doom II: Hell on Earth*
Marine Suit – Finish No Rest for the Living
Doom II T-Shirt – Finish any level
Duke Nukem: Manhattan Project*
Jet Pack – Finish the game
T-Shirt – Complete any level[/details]
E [details=Open Me]Earthworm Jim HD*
Earthworm Jim Shirt – Defeat Billy
Earthworm Jim Supersuit – Complete any bonus stage[/details]
F [details=Open Me]Fable III*
Crown – Become the king of Albion
Royal Boots – Win the support of the Dwellers
Royal Shirt – Win the support of Bowerstone
Royal Trousers – Win the support of the Swift Brigade[/details]
G [details=Open Me] Guitar Hero: Warriors of Rock*
Demigod Helmet – Free the Demigod
Guitar Hero Shirt – Play One Song
Johnny’s Jacket – Earn 1,500 Stars
Legendary Guitar – Obtain the Legendary Guitar
Soundgarden Shirt – Play Black Rain[/details]
H [details=Open Me]Halo Waypoint*
EVA Helmet – Achieve all career milestones
Monitor Pet – Start Halo Waypoint
ODST Armor – Unlock Halo 3: ODST’s Good Samaritan achievement
ODST Helmet – Unlock Halo 3: ODST’s Campaign achievement
ODST Hoodie – Unlock Halo 3: ODST’s Dark Times achievement
ODST Shirt – Unlock Halo 3: ODST’s Tourist achievement
Recon Helmet – Unlock Halo 3: ODST Vidmaster Endure achievement
Halo Reach*
Carter’s Helmet – Clear a campaign mission on Legendary difficulty without dying
Emile’s Helmet – Earn a Bulltrue medal in multiplayer or Firefight matchmaking
Jorge’s Helmet – Earn a Killtacular medal in multiplayer matchmaking
Jun’s Helmet – Kill 100 enemies in a row without dying in campaign or Firefight
Kat’s Helmet – Avenge a teammate’s death in multiplayer matchmaking
Noble 6 Helmet – Available to attendees of 2010 Gamescom, PAX, or San Diego Comic-Con
Hydro Thunder Hurricane*
Hydro Thunder T-Shirt – Earn 800 points from events
Toy Boat – Earn 18,5000 Points[/details]
I [details=Open Me] Ilomilo*
Ilomilo T-Shirt – Complete three levels
Ilo & Milo Pets – Unlock a full memory[/details]
J [details=Open Me]Kinect Joy Ride*
Aviator Goggles – Play each activity
Boss Hoodie – Race on All Tracks
Marathon Racer Suit – Play for 10 hours
Raven Jacket – Drive every vehicle
Smashing Helmet – Play each activity 10 times[/details]
K [details=Open Me]Kinect Adventures*
Adventurers Outfit – Participate in the Ultimate Treasure award ceremony
Gloves – Participate in the Treasure Grab award ceremony
Sunglasses – Participate in the Chasing the Sun award ceremony
Sweatband – Participate in the Gearing Up award ceremony
Watch & Band – Participate in the Winning Time award ceremony
Kinectimals*
Bengal Tiger T-Shirt – Visit The Glade
Cheetah T-Shirt – Visit La Selva
Leopard T-Shirt – Visit Cherry Blossom Grove
Lion T-Shirt – Visit Fiddler’s Beach
Panther T-Shirt – Visit La Sun Mountain
Kinect Joy Ride*
Aviator Goggles – Play each activity
Boss Hoodie – Race on All Tracks
Marathon Racer Suit – Play for 10 hours
Raven Jacket – Drive every vehicle
Smashing Helmet – Play each activity 10 times
Kinect Sports*
I Love Kinect Sports T-Shirt – Secure the Champion Sports Badge
Kinect Sports Cap – Secure the Amateur Sports Badge
Kinect Sports Star T-Shirt – Secure the Master Sports Badge
Kinect Sports T-Shirt – Secure the Professional Sports Badge
Kinect Sports Trophy – Secure the Legendary Sports Badge[/details]
L [details=Open Me] Lara Croft and the Guardian of Light*
Mercenary Outfit – Complete the game (different outfit for male and female avatars)
Lazy Raiders*
Dr. Diggabone’s Hat – Collect 16 relics
Dr. Giggabone’s Outfit – Start the game
Left 4 Dead 2*
Bull Shifters Shirt – Win 10 games in Verses
Depeche Mode Shirt – Hold and rescue Gnome Chompski from Dark Carnival
Gnome Pet – Play six mutations (requires The Passing DLC)
L4D2 Hat – Play any map in The Passing
L4D2 Shirt – Win 10 Scavenge games
Med Kit – Beat all five campaigns
Zombie Hand Shirt – Kill 10,000 infected
Limbo*
Limbo Pet – Beat the game
Limbo T-Shirt – Earn your first Limbo Achievement
Lips*
Over the Top Hat – Play one song
Lady Gaga Shades – Earn 100 of every type of medal and 100,000 stars
Infinity Shades – Earn infinity on a song
Lips: I Love the 80s*
Chillin’ Blazer – In Relax, achieve a Big Bang rating
Devo Outfit – In Whip It, achieve a Big Bang rating
Lips: Party Classics*
Biker Guy/Gal – In YMCA, perform all gestures and get a Big Bang rating
Teen Sensation – In I Think We are Alone Now, perform all gestures and earn a Big Bang rating[/details]
M [details=Open Me] Magic: The Gathering – Duels of the Planeswalkers*
Magic the Gathering Cards – Unlock all cards for six decks
Planeswalkers T-Shirt – Unlock all cards for three decks
Major League Baseball 2K10(MLB 2K10)*
2K Sports Jersey – Win a game in any mode
Bat and Ball – Hit 150 homers, or win the batting title in Franchise or My Player modes
Batting Helmet – Hit a grand slam
Evan Longoria Jersey – Win the best fielder award in Franchise or My Player modes
MLB 2K10 Jersey – In My Player, get called up to the Majors
Monday Night Combat*
Mascot Mask – Meet the mascot during the tutorial
Monday Night Combat Shirt – Complete Exhibition Blitz mode[/details]
P [details=Open Me] Perfect Dark*
Elvis Plushie – Beat the game and complete a special mission
Perfect Dark Shirt – Achieve a headshot
Pinball FX 2*
Pinball FX 2 T-Shirt – Achieve 5,000 Wizard Score
Pinball FX 2 Wizard Robe/Sorceress Dress – Achieve 100,000 Wizard Score[/details]
R [details=Open Me] Raskulls*
Giant Crown – Complete a mega-challenge in chapter 2
Radskulls T-Shirt – Complete a mega-challenge in chapter 1
Red Dead Redemption*
Gentleman’s Attire/Ladies Finest – Complete the Skin It To Win Challenge in the Social Club
Rockstar T-Shirt – Find the hidden chest in Riley’s Charge
Sombrero – Shot an enemy’s hat off without killing them
Red Dead T-Shirt – Open the chest in the Marston household’s attic
Risk: Factions*
Risk T-Shirt – Finish the game
Robot Head – Finish the game
Rock Band 3*
Bass T-Shirt – 5 star 25 rock band 3 songs on Easy bass (or 3 star on higher difficulties)
Drum T-Shirt – 5 star 25 rock band 3 songs on Easy drums (or 3 star on higher difficulties)
Guitar T-Shirt – 5 star 25 rock band 3 songs on Easy guitar (or 3 star on higher difficulties)
Keyboard T-Shirt – 5 star 25 rock band 3 songs on Easy keys (or 3 star on higher difficulties)
Microphone T-Shirt – 5 star 25 rock band 3 songs on Easy vocals (or 3 star on higher difficulties)[/details]
S [details=Open Me] Scrap Metal*
R/C Car – Complete all single player missions
Scrap Metal T-Shirt – Complete your first race
Snoopy Flying Ace*
Red Baron Avatar Outfit – Achieve the Flying Ace rank
Snoopy Avatar Shirt – Earn a medal on all missions
Sonic Adventure*
Blue Sonic T-Shirt – Play for five hours
Sonic Shoes – Play for ten hours
Sonic the Hedgehog 4: Episode 1*
Sonic Costume – Finish the game
Sonic Mask – Defeat Eggman in E.G.G. Station, then collect all the rings in the ending sequence
Sonic Free Riders*
E-10,000 G Shirt – Playing as E-10,000 G, finish first in every race
Jet Shirt – Playing as Jet, finish first in every race
Sonic Shirt – Playing as Sonic, finish first in every race
Sonic Free Riders Shirt – Watch all of the credits
South Park Let’s Go Tower Defense Play!*
Cartman’s Hat – Complete one level
Kenny’s Hoodie – Complete the campaign
'Splosion Man*
Big Science Shirt/Dress – Complete the multiplayer campaign
’Splosion Man Shirt/Sweatshirt – Break any glass object
Super Meat Boy*
Super Meat Boy Prop – Beat Light World
Super Meat Boy T-Shirt – Unlocked through time spent in the game. Exact hours have not been nailed down yet[/details]
T [details=Open Me]Toy Soldiers*
Gas Mask – Complete the first level
Pickelhaube Hat – Finish the campaign[/details]
U [details=Open Me] Unbound Saga*
Unbound Saga Comic Book Stack – Complete Story mode
Unbound Saga T-Shirt – Complete any episode[/details]
W [details=Open Me] Nothing [/details]
Y [details=Open Me] You Don’t Know Jack*
Bald-Headed Ski Mask – Play episode 58
Bill O’Brien Doll – Find the wrong answer in episode 73
Pants – Play episode 9
You Don’t Know Jack T-Shirt – Play any episode[/details]
D
