For almost every project I've worked on I have created tools to improve my workflow and the workflow of my teammates. These tools include, but are not limited to:
Add coloured dividers to your Unity hierarchy to better organise often unwieldy scenes.
Quickly change between scenes in your project directly from your scene view, rather than constantly sifting through the project window to find the scenes you use frequently.
Create customisable keyboard layouts quickly. Designed for VR, but created in a generic way that can be used for any platform if necessary.