All of the sample apps listed here use the Flutter Scaffold class in an interesting way. The Sample App Catalog page lists all of the sample apps.
A typical AppBar with a title, actions, and an overflow dropdown menu.
This app features the following classes: AppBar, IconButton, PopupMenuButton, Scaffold.
An AppBar with a TabBar as its bottom widget.
This app features the following classes: AppBar, DefaultTabController, TabBar, Scaffold, TabBarView.