For me there are two.

1. Audio Bookshelf client, it's in test flight but so far it's been awesome.
2. Jellybox, a Jellyfin music client, haven't tried it yet as I've just heard of it, but the screenshots look a lot better then FinAmp.

Most recently, Sink It for Reddit. While I don’t go on reddit regularly anymore, I still check on my city’s sub from time to time. Sink It makes the mobile web version of reddit more tolerable and removes sponsored content. So you get a better browsing experience without having to install their official app.