PPSSPP
PPSSPP is a free and open source, multiplatform PSP emulator that can run games with full HD resolution
GB Enhanced+ is a free and open source a Game Boy emulator
DuckStation is an simulator/emulator of the Sony PlayStation(TM) console, focusing on playability, speed, and long-term maintainability
Dolphin Emulator is a free and open source multiplatform emulator for the two latest Nintendo game consoles: GameCube and Wii