HTTP
The Dart team's HTTP packages are the most popular on pub.dev. They provide a high-level API that can make dealing with network activities easier on mobile, desktop, and browser platforms.
SQFlite
On both Android and iOS, SQFlite is one of the most popular and up-to-date libraries for connecting to SQLite databases in Flutter. The path package includes utilities for specifying where the database should be saved on disk.
Package Info Plus
Basically, this is a querying API for getting information like CFBundleVersion on iOS and versionCode on Android. Android, iOS, MacOS, Web, Linux, and Windows are all supported.
URL Launcher
This is a tremendously useful package for launching absolute or relative URLs in web browsers, map apps, dialer apps, and mail apps for iOS and Android. This plugin creates intents that open applications using various URL schemes.
Path Provider
Path Provider is used to identify locations often visited on iOS or Android. It includes a Temporary and Application Documents Directory that supports both internal and external storage, making it easier to locate private and public documents.
Video Player
On Android, iOS, and the web, this is used for showing inline video with other Flutter widgets. It can play videos from three different places: assets, files, and the internet.