Any app that doesn’t require any backend to function.
If you ask for a subscription for an app without the need to support a backend… I won’t subscribe. I’ll find something else.
Mostly anything else is fine.
Though, if it’s something like a Note-Taking app where the cloud infrastructure for backups and sharing would cost pennies and you’re asking more than $1 a month, I’m out. Looking at you, Evernote. $64 a year to replace the built-in Notes app? No thanks.
Don’t screw over small indie devs.