DOSBox is an emulator that recreates a MS-DOS compatible environment (complete with Sound, Input, Graphics and even basic networking).
With BlueStacks App Player, you can install Android APK files and run apps like Pokemon Go, WhatsApp, Instagram, and Snapchat on your Windows PC!
Realistic racing game with wonderful graphics
FlightGear is an open-source flight simulator. It is developed by skilled volunteers from around the world.