This is a cool topic. I have some codes too. I will qualify that some of these are probably pushing 10 years old, so it’s entirely possible they are not accessible or something. No idea. XD But we can try!
Sonic the Hedgehog 4 Ep. 1 (Steam)
The Land of Pain (Steam)
Resident Evil (2002) HD (PS4)
Wolf of the Battlefield: Commando 3 (PS3)
Citizens of Earth (WiiU)
The King of Fighters 2002 Unlimited Match (Steam)
The Last Blade (Steam)
Metal Slug 2 (Steam)
Metal Slug 3 (Steam)
Shock Troopers (Steam)
Twinkle Star Sprites (Steam)
Beware Planet Earth (Steam)
Peggie, Bookworm, Bejeweled 3 (Origin)
Forward To The Sky (Steam)
Zenith (Steam)
Think of The Children (Steam)
Hive Jump (Steam)
Warhammer: End Times – Vermintide (Steam)
Monster Slayers + DLC (Steam)
Toren (Steam)
Dungeons 2 (Steam)
Infectonators: Survivors (Steam)
Still Not Dead (Steam)
Space Hulk Ascension (Steam)
Mytheon (Steam)
The Warlock of Firetop Mountain (Steam)