Invision - Prototyping and collaboration for design teams
Xamarin.Android - Integrated environment for building not only native Android but iOS and Windows apps too.
Proto.io - Create fully-interactive high-fidelity prototypes in minutes that look and work exactly like your app should. Sign up for a free 15-day trial and get started.
Qt Creator - Qt Creator is a cross-platform C++, JavaScript and QML integrated development environment. It is the fastest, easiest and most fun experience a C++ developer could wish for.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Rider - Rider is a cross-platform .NET IDE based on the IntelliJ platform and ReSharper.