What non-FOSS software have you been unable to quit?
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.
Google Maps. It sucks, and stores randomly pop in and out while you're trying to zoom in past the McDonalds ad that's showing despite you searching "shoe store", but it has so much more info than the competitors that they don't compare.
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.
Unfortunately OSM won't be able to compete with user reviews for example (except if we steal those from Google). Also a bunch of shops can't be seen there, which is crucial for me to discover cheap restaurants.