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.
OSMAnd is good in many ways (and has come a long way too), but the app suffers from too many settings and too much menu diving for my taste. OrganicMaps is good because it’s like having “OSMAnd lite.” Used to be that without Google Services that there was no voice navigation, but now I’m able to use RH Voice with Organic Maps. MagicEarth is another map navigation app, but not open source.
I’ve really enjoyed using MagicEarth. I’d probably move to Organic Maps if they implemented routing for other public transport besides trains.