I’m an iOS musician.
AUM is an absolute MUST as well as it’s companion app
AudioShare. I also use
MultiTrack DAW (stable and very finger friendly) but perhaps not as full featured as
Auria. I’m not a huge fan of Cubasis. Seems like they crammed too much visually and it’s sort of a UI overload. Every time I use it I want to go back to Multitrack again.
JamUp Pro for my bass and guitar amps (as well as pedal effects). Some really well done emulations. Though, not sure if it’ll be supported as they’ve moved more over to their Bias Amp and effects apps.
I can’t say enough great things about AUM.
Similarly,
Audiobus too.
For stufff that isn’t music related,
GoodReader is basically a filesystem for your iPad. Very well done.
Also,
Workflow (which Apple bough and is transforming into Shortcuts in iOS12)
Pixelmator,
Filmic Pro,
Motiv Video (and Audio),
Sketches Pro