The only tool being an absolute given to me is my “Better column navigation” - https://forum.renoise.com/t/new-tool-3-1-better-column-navigation/46034
It’s just a small patch to fix the “broken” tab behavior in the Renoise pattern editor.
Other than that, it depends on what I feel like doing 
I don’t have any other tool that I rely on all the time, or that I feel I must have installed.