Here is a small list of applications for the iPhone (iOS), which I have compiled from my own experience.
I recommend deleting applications that are not in use, as they will be periodically updated, it is possible to use the resources of the phone, make Internet connections with server, consume a little battery power, etc.
Google Maps – you can pre-download offline maps, convenient satellite photos and pedestrian navigation.
maps.me is a simple offline navigator, I use it as a backup.
CityGuide is a paid but very convenient navigator for a car with offline maps, reports on pedestrian crossings, cameras, speeding, gas stations and a lot of other things.
Google Street View is an application for viewing and creating 360-degree photos, photos are saved to the phone and can be published in Google Maps.
Google Translator is the best translator, you can download languages for offline translation, it works as a text and online audio and online video translator (when the camera is on, it displays the translation in real time on the screen).
Google Authenticator is a great two-factor authentication app that can be configured with almost any service.
iNetTools are simple network tools like ping, trace route, dns lookup, port scan, whois, lan scan, etc.
Termius is a convenient SSH and Telnet client
iDMSSLite is an application for viewing Dahua cameras, it is possible to view the recorded video.
Nike Run Club and Nike Training are great running and workout apps that work well with AppleWatch.
Duolingo is the best free app for learning foreign languages in my opinion, it also works through a browser.
Yazio is a free food tracking app that finds products by barcode or search.
Zoiper, Softphone – sip clients for connecting to the astersik server.
Ajax is an application for managing the best alarms, controlling electrical appliances, viewing the temperature in rooms, etc.
Pages – I use to make a list of tasks.
Nextcloud is a personal cloud that can be run on a server with any disk space.
Popular messengers: Skype, Viber, Telegram, Facebook, Messenger, etc.
I prefer to read email through a standard email client in iOS.