For me, Google video search, Google books (Internet Archive is good, but doesn’t always have the same stuff), Adobe InDesign (but in the process of learning LaTeX), and Typewise. As for the Google stuff, I liked Whoogle a lot, but almost all their instances seem to have been blocked or shut down. Also, apologies if this is repeating an earlier post.
I don’t understand why we spend so much time praising proprietary software in these communities.
As to your question, I have a separate Windows machine for gaming, but that’s it. I keep one foot in the free world and one in the proprietary. As for productivity tools I can’t think of a proprietary tool I “can’t quit” or that I would pick in favor of a free tool.
Fans of proprietary software have this weird belief that free software users choose inferior tools for purist or idealist reasons. This is offensively ignorant. No one chooses bad tools on purpose; we just consider freedom to be part of the criteria of a good tool.