Blender!

• Sublime Text 3, cool code editor: https://www.sublimetext.com/3
• Blender, free 3D model editor: https://www.blender.org/
• MagicaVoxel, free VoxelArt (3D models) editor and renderer. Easier than Blender: https://ephtracy.github.io/
  
• PixelArt Editors: https://lospec.com/pixel-art-software-list (the lospec site also contains many useful pixelart palettes)
• Sound generator for your game: https://www.bfxr.net/
• For mindmaps and creating concepts:  https://github.com/juzzlin/Heimer
• If  you prefer to create music by tracker-like approach: Renoise https://www.renoise.com/
• Map editor, supported by many game engines: Tiled https://mapeditor.org/
• You should also use some task manager, for example Trello. Or just a plain text todo list.
• Game idea generator: http://orteil.dashnet.org/gamegen

Bonus:

TIC-80 - not as cool as Godot, but it's a fantasy computer that can be used to create minigames, definitely worth checking: https://tic.computer/