You can make use of the operating system's own text-to-speech systems, either as an accessibility feature or to create old-school voiced games. https://docs.godotengine.org/en/stable/tutorials/audio/text_to_speech.html It apparently should work out of the box on Windows and MacOS, but not all Linux distros will have the proper packages pre-installed.

This "name-something" functionality for import of 3D scenes is quite handy. https://docs.godotengine.org/en/stable/tutorials/assets_pipeline/importing_scenes.html

I don't know if shaders fall into this category, because everyone knows that it exists but I always feel like many people are afraid of trying to work with this and so just skip this entirely... And of course this is not limited to Godot.

The way that you can put a 3D camera and world inside a resizeable UI viewport container is really cool. I was able to make like a handheld console UI and just add the 3D view where the screen would be. Similarly the way you can make things in a 2D scene and then put it as a plane in a 3D world.