It's exactly as it states. I want to make a list of every game on GOG that comes with an editor, either in game or as a separate application. This list will be updated for as long as I keep hearing of new games. Please give me games that you know of that include an editor and follow these two rules.

The rules are:
- Both the editor AND the game must both be available currently on GOG.com
- It has to be official, no fan tools or anything unofficial

1. Age of Wonders Series
2. Broforce
3. Caesar Series (and its related city-building games)
4. Civilization Series
5. Combat Mission: Beyond Overlord
6. Cultures 3 and Eighth Wonder of the World (First two games may not have one)
7. Delta Force Series
8. Descent 3 (sadly the editors for the first two are not available here)
9. Divinity Original Sin Series (The other Divinity games do not have an editor)
10. Dragon Age Origins
11. Dungeon Keeper 2
12. Empire Earth Series
13. Fallout 3 and New Vegas
14. Far Cry
15. Forgotten Realms: Unlimited Adventures
16. Freespace Series
17. Ground Control Series
18. Hammerwatch
19. Heroes of Might and Magic Series
20. Homeworld 1 and 2
21. Hotline Miami 2
22. Impossible Creatures
23. Jazz Jackrabbit 2
24. Legend of Grimrock Series
25. Moto Racer 2 (EDIT: Thanks Chevkoch!)
26. Neverwinter Nights Series
27. Railroad Tycoon Series
28. Rayman Forever
29. Rollercoaster Tycoon 2 and 3 (First game strangely lacked a scenario editor)
30. Rune Classic
31. Serious Sam 1 and 2
32. SimCity 2000 and 3000
33. Space Empires IV
34. Spellforce 1 and 2 (not sure about 3)
35. Star Wars Galactic Battlegrounds
36. The Elder Scrolls III and IV
37. The Incredible Machine Series
38. The Settlers 2 10th Anniversary
39. The Witcher 2
40. Tomb Raider Chronicles
41. Torchlight Series
42. Total Annihilation
43. Turok Remastered
44. Unreal Series
45. VVVVVV
46. War for the Overworld
47. Warlords Battlecry Series
48. Worms Series

Hotline Miami 2 has a level editor and War for the Overworld has a map editor. Pretty sure that Heroes of Might and Magic 2 and 3 also have map editors.

Edit: Divinity: Original Sin also has a level editor.

Zeus and poseidon
Cultures at least in 8th wonder of the world but won't check other cultures game since i don't have them installed
Total annihilation commander pack

Thank you, both.

I honestly did not expect this list to get so big already.

I believe VVVVVV has an editor. (I don't actually own the GOG version, but my Humble Bundle version contains the editor, and it's accessed by a menu within the game, so I would expect the editor to be in the GOG version.)

Quake, Quake II, Quake III Arena, Shadowrun Returns, Shadowrun: Dragonfall, Shadowrun: Hong Kong, Star Wars: Jedi Knight - Jedi Outcast, Star Wars: Jedi Knight - Jedi Academy, System Shock 2, Thief: The Dark Project and Thief II: The Metal Age have official mapping tools/editors.

I have the quake series and there are no level editors that I can see with the GOG release. For this list the tool must come with the GOG version and not separately.

Hammerwatch. There are fantastic mods created with the included editor for it, Dingovania is one that I feel offers a more interesting campaign than the ones coming with the base game.

EDIT: Oh, and I can confirm Moto Racer 2 has an editor included. I made a track with that myself, works beautifully.

Hammerwatch is a weird looking one. Its added.

Thanks for confirming Moto Racer 2. Glad you could get it running, I sure couldn't.

I was about to make a few suggestions based on a similar thread I created some years ago, but then I realized I couldn't say for sure if the editors are included on GOG or just downloadable from the games' websites or something (e.g. Driftmoon, Blades of Avernum - included in Avernum: The Complete Sage, The Witcher 1, Amnesia: The Dark Descent etc).

So here's a different kind of suggestion: If you'd sort the games in the OP alphabetically, that would make it easier for others to check whether the games they can think of are already on your list or not!

Railroad Tycoon 2 & 3 both have inbuilt scenario editors.

Does SimCity count? 2000 has the SCURK program which is about as directly into editing as you can get, 3K has the BAT but no direct ingame editor, and 4 has the ability to edit terrain before entering Mayor mode.

Caesar has inbuilt editing for scenario creation.

Does SimplePlanes count? You can't change the terrain, but the whole point is to build your own planes out of building blocks.

Serious Sam has a very advanced editor built in the directory of the game.

Impossible Creatures has a mission editor where you can build missions with the same tools the devs used.

I'm aware that Settlers 2 10th aniv edition has a map editor, but I'm not sure about the rest of the series.

Re-Volt, while no longer sold, has a track editor.

Space Empires IV has a built in map editor.

Added almost everything you said. Honesty I had no idea that Serious Sam ever had an editor. Why don't they advertise that?

I am not counting SimCity 4 becuase it has no official tool, that I know of, to add your own content to the game (buildings, scenarios, etc.) or alter anything about the game. That's also why I would not count Simple Planes.

Thanks!

Also
Taken care of. Thanks for the suggestion.

EDIT 2: Does anyone know if Red Faction includes its editor here? I remember it having one but can't find out if it is included in the GOG release.

Hammerwatch's looks like being a really powerful one from what I've seen in tutorial videos on YouTube. Not tried it myself though, as it would demand a serious time commitment to build a decent campaign I think.

Too bad you had problems with the editor for Moto Racer 2; it's on the feature-light side, but quite easy to work with.

Die by The Sword has a move editor listed on its game card:

"Includes the original Die by The Sword and it's expansion Limb from Limb along with the move editor for both games"

Also The Witcher 1, I think. I haven't used it but there's a link in thr launch menu, and the Enhanced Edition came with some fan-made adventures included.