Godot Engine - Feature-packed 2D and 3D open source game engine.
Android Studio - Android development environment based on IntelliJ IDEA
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
Xcode - Xcode is Apple’s powerful integrated development environment for creating great apps for Mac, iPhone, and iPad. Xcode 4 includes the Xcode IDE, instruments, iOS Simulator, and the latest Mac OS X and iOS SDKs.
BYOND - BYOND is the premier community for making and playing online multiplayer games.
Adobe AIR - Adobe® AIR® runtime enables developers to package the same code into native apps for Windows and Mac OS desktops, iPhone, iPad, Kindle Fire, Nook Tablet & Android. Buy now.