The games below are the standout deals imo in terms of price and popularity, links are:
Sonic and All-Stars Racing Transformed $14.99 (new low)
http://www.greenmangaming.com/s/au/en/pc/games/racing/sonic-…
Sanctum 2 $14.99 (new low)
http://www.greenmangaming.com/s/au/en/pc/games/strategy/sanc…
Sniper Elite: Nazi Zombie Army $14.99
http://www.greenmangaming.com/s/au/en/pc/games/action/sniper…
Chivalry: Medieval Warfare $24.99
http://www.greenmangaming.com/s/au/en/pc/games/shooter/chiva…
Use GMG20-4B9NY-L4FEN for an additional 20% off; keep in mind these are four keys each. All the above are Steamworks games, and I believe the rest are too - there will be a notification under the images.
There are more packs on sale though, you can use http://www.greenmangaming.com/search/?q=4%20pack to search for the rest like EVE, Dollar Dash, Frozen Synapse.
Lastly, feel free to use my referral link http://www.greenmangaming.com/hot-deals/?gmgr=sovojeyu for $2 GMG credit each after a first purchase over $2.
4 pack for sonic all stars racing?? wow… now to find some friends…