Here is my short personal toolset, which I'll use during the jam:

• Godot Engine - my engine of choice, it's very flexible and fast enough for rapid game development. However, GMS is also good.
• VS Code - despite having some small troubles with it, it's an excellent external IDE for Godot. I prefer using it with JetBrains Mono font, Darcula colour theme, TODO tree and Better Comments extensions.
• Git Kraken - I like this git client, as it also includes fine boards for task tracking.
• Asesprite - just a great editor for pixel-art assets.
• Affinity Designer - it's the best paid vector art editor in the world.

Good luck and have fun during the jam, you are all absolute legends.