[hattar]

Keepass, Calibre, and 7-zip come to mind.

[moonchrome]

I won't argue these projects aren't quality because they certainly do the job, but they obviously lack polish of commercial software. Eg. despite looking into kepass I still chose to pay for 1password, just for the convenience.

[SalamiMoon]

VLC and OBS as well.

[moonchrome]

VLC is a good point I forgot about it. AFAIK OBS is sponsored by streaming platforms - I think it's another case of comoditizing the infrastructure.