Steam Holiday Sale: The Great Gift Pile - How does it work?

Steam is dearly loved by many for its absolutely stellar discounts around Christmas.

This year, they have pulled "The Great Gift Pile" out of the bag as well as the usual amazing discounts on games and dlc packs.

The Great Gift Pile sounds good, but what is it?

The Great Gift Pile is an incentive to do certain things in games to get achievements that have been made especially for The Great Gift Pile.
Each day, there will be around 10 games that you can play (if you own them of course), and when you do a certain thing in the game, you earn an achievement and a prize.
For example, from simply checking my steam inventory, I received a 50% off voucher for any of valves games. That is pretty awesome.

You could win a massive amount of things from this, what people have claimed to have won so far are:

~ Game rewards ~
- Half Life 1- Half Life 2 Episode 1- Half Life 2 Episode 2 - Portal 2- Counter Strike: Source- Coal- Half Life 2 episode 1Half Life 2 lost coastHalf Life 2 DeathmatchHalf life Deathmatch: Source * All one gift *- Portal 1- Day of Defeat: Source- Frozen Synapse- The Orange Box - Sherlocke Homes games- Overlord, Overlord II, and Overlord: Raising Hell * All one gift *- Killing Floor- Lego Batman: The Videogame
Tropico 3 - Steam Special EditionTropico, Tropico 2: Pirate CoveTropico 3: Absolute Power * All one gift *- Men Of War: Assault Squad- Oddworld: Abe's Oddysee- Monkey Island Complete Pack- Chantelise- Mafia- Greed Corp- The Binding Of Isaac with Soundtrack- Orcs Must Die - Gemini Rue- DotA 2- Worms Reloaded - Oddworld: Strangers Wrath- Left 4 Dead 2 - FARMING SIMULATOR 2011- Runespell: Overture- Saints Row: The Third- Sniper: Ghost Warrior + 2 DLC- AI War: Fleet Command - Sega genesis classics collection - Gothic 4- Trine- Batman Arkham Asylum- Braid- X2: The ThreatX3: ReunionX3: Terran ConflictX: Beyond the FrontierX: Tension, X3: Albion Prelude * All one gift *- VVVVVV- Tom Clancy's H.A.W.X.® 2- Two Worlds II- Demolition Inc.- Freedom Force- Vegas: Make It Big- Risen - The Witcher: enhanced directors cut- A.R.E.S.- Civilization IV- Wonderful End of the World- Dead Island- Battlefield: Bad Company 2- FlatOut: Ultimate Carnage- Shadowgrounds + Shadowgrounds survival- X3: Gold - Payday: the heist- Magicka- Rome: Total War™ - Gold- Left 4 Dead- Left 4 Dead 2- FEAR Complete Pack (ROW)- Storm:Frontline Nation

~ Coupon gifts ~ - 10% off Sega titles- 10% off Warner Bros Coupon- 10% off any DeepSilver title- 10% off any bitComposer- 10% off Paradox games - 10% off Meridian4 games- 10% off Valve titles


- 25% off All Valve games- 25% off Codemasters coupon- 25% off Activision games- 25% off Atari game- 25% off Square Enix titles- 25% off iD games - 25% off KalypsoMedia- 25% off Bethesda- 25% off Hoard- 25% off any thq titles except for the upcoming Darksiders 2- 25% Konami Games 


- 33% off all Valve games- 33% off Cities XL 2012- 33% off 2K games- 33% off Renegade Ops- 33% off Skyrim - 33% off driver SF- 33% off id Super Pack- 33% off Game of thrones Genesis 


- 50% off all Valve games- 50% off penny arcade- 50% off Fallout Collection- 50% off Lightfish game - 50% off Stalker: Clear Sky- 50% off Anomaly Warzone Earth- 50% off Fallout 3- 50% off on Rock of Ages- 50% off any Jamestown title- 50% off F12011- 50% off Zeno Clash- 50% off Brink - 50% off LIMBO- 50% off The Graveyard- 50% off Drakensang - 50% off Kane & Lynch 2- 50% off Sam and Max pack - 50% off Munch's Odyssee- 50% off Mumbo Jumbo complete pack- 50% off on Dungeons of Dredmor- 50% off L.A. Noire- 50% off Oddboxx- 50% off beat hazard complete pack- 50% off max Payne 2- 50% off FEAR 3- 50% off Trainz Simulator 12- 50% off Rockstar titles- 50% off From Dust - 50% off Operation Flashpoint: Red River- 50% off Nordic Games- 50% off Steel Storm: Burning Retribution (4-pack)- 50% off Sol Survivor- 50% off Droplitz- 50% off Universe Sandbox - 50% off Borderlands GOTY- 50% off of Recettear: An Item Shop's Tale- 50% off VirtualTennis4 - 50% off Worms Crazy Golf - 50% off King's Bounty Platinum- 50% off Block that matter- 50% off Doom 3- 50% off Homefront- 50% off 1,2,3, Kick It- 50% off EDGE- 50% off Xotic- 50% off Solar 2- 50% off Grand Theft Auto: Vice City- 50% off hacker evolution: untold - 50% off SEGA Classics collection- 50% off Sequence- 50% off Recettear: An Item Shop's Tale- 50% off AlienBreed3: Descent- 50% off Shadowgrounds Survivor- 50% off Combat Wings: Battle of Britain- 50% off X3: Gold- 50% off Total War: Shogun 2- 50% off Hoard - 50% off binding of Isacc- 50% off The Witcher: Enhanced Edition- 50% off Bioshock 2- 50% off Civilization 5 - 50% off section 8: prejudice- 50% off of Wings of Prey- 50% off APOX- 50% off Orcs Must Die- 50% off any ID game - 50% off Portal 2- 50% off Magic: The Gathering - Duels of the Planeswalkers 2012- 50% off Warhammer 40,000: Dawn of War II Retribution - 50% off of Doom 3- 50% off Bunch of Heroes- 50% off Abe's Oddysee- 50% off Monday Night Combat- 50% off Dwarfs! - 50% off Dino d-day- 50% off Nail'd- 50% off Atari gold coupon - 50% off of Darwinia


- 60% off King Arthur Franchise. - 66% off Prototype



- 75% off risen- 75% off Napoleon Total War- 75% off Garrysmod- 75% off CoD4- 75% off Sacred 2 - 75% off Torchlight 

That list of games is from a Steam forums thread started by Valestrum, props to him for compiling this list.