Starting this thread with C# stuff I use on Unity and the equivalent for #godotEngine C# I am learning on the way, maybe there is more suggestions or corrections to what I share:
Using Unity Vector3.ProjectOnPlane with Godot
Getting transform vector normal Up, Forward and Right with Godot
Using Unity Vector3.Angle with Godot
Godot Node3D.LookAt instead of Unity Transform.LookAt to make an object/node points forward the target position

Godot Basis.LookingAt instead of Unity Quaternion.LookRotation helpful to make an object/node Z axis point in the same direction as the vector is given.

No idea if is possible to get an Vector3 from the Basis to assign the value directly on Node3D.GlobalRotation

I just realize this is not the bes example lol, you can just grab Basis to one Node3D and add to another, but you get the vector idea.
Godot Vector3 Lerp could a be a little different to use compared to Unity one, this works for Vector2 and you can still use Mathf.Lerp for floats similar to Unity one.
Godot Quaternion instead of Unity Quaternion.AngleAxis to rotate around the given axis