Summary:
GOG database (these games were detected a long time ago, they were probably scrapped for some reason):
Hummingwarp Interactive - Secret Little Haven
Sonalysts - Fleet Command, Sub Command, Dangerous Waters, 668(I) Hunter Killer
Something We Made - Toem
拾英工作室 - Tales of the Black Forest
Random Games Inc., MPS Labs - Wages of War (?)
Sub-forums:
Serious Sam 2 (Now hidden)
Serious Sam 3 (Now hidden)
Hidden GOG data:
Mafia: Definitive Edition
Senran Kagura Shinovi Versus
Lumberhill
HITMAN 2 Gold Edition
Prince of Qin
Pronty
Roguebook
GOG logo on websites/trailers:
The Lost Wild
Blight: No Man's Land
Crisis in the Kremlin
PRIM
Frozenheim
Warhammer 40,000: Rogue Trader
Press sites:
Fata Deum
World Championship Boxing Manager II
SunnySide
Miasma Chronicles
Trinity Trigger
Discord, Twitter (The dev has already contacted GOG):
ANNO: Mutationem
SCORN
Eiyuden Chronicle: Hundred Heroes
The Darkest Tales - Into the Nightmare
Szrot
Forest Grove
Drova - Forsaken Kin
Meat Puppet
INCANTAMENTUM
Sea Dogs: Legendary Edition
darkwebSTREAMER
Future Fragments
Westwood Shadows
Brutal Orchestra
Unfortunately Ninja
Chronicles of 2 Heroes
Discord, Twitter (The dev would like to):
REKKR: Sunken Land
Instruments of Destruction
Islands of the Caliph
Dangerous Dave: Champion's Edition
Dying Breed
XEARZ
Spire of Sorcery
Supplice
Madshot
Coromon
Dune: Spice Wars
Prehistoric Kingdom
Trial Out
Dark Quest: Board Game
Wildermyth
Wizordum
Let Bions be Bygones
Voodoo Detective
Legacy hidden GOG data (these games were detected a long time ago, they were probably scrapped for some reason):
Assassin's Creed 2
Assassin's Creed 3
Skyrim
Civilization V
Wages of War
Army Men: Air Tactics
Army Men: Sarge's Heroes
Army Men: Sarge's War
The Abbey
RAGE
Culpa Innata
Battle vs Chess
Fleet Command
Bound By Love