Gonna go with Firefox as both my most-used piece of open-source software, and the software I see as most important to its ecosystem. If Firefox fails then we’ve just got Chromium-based browsers and, I guess, Safari.

LibreOffice is equal to any office software out there, and has been much more stable than OpenOffice, and works without an internet connection unlike Google Docs.

Blender by a huge mile. Yes, there’s tons of other software like Linux, of course, but Blender is such a powerful, well managed, economically viable and healthy (community) project that it should be shown as an example of how Open Source should be.

My biggest hurdle with other projects is the fanboys, because many times they’re quite toxic, insulting everybody who doesn’t adore the project and don’t accept constructive criticism.

uBlock Origin, it’s not even close!

I love and use Bitwarden daily.

Signal, Thunderbird and Bitwarden

Firefox and its derivatives. They’re the last free bastion preventing a Chromium monopoly on the browser market, which is hugely important - especially these days with Google’s push for Mv3.