WineHQ Emulator.

Wine for running Windows apps under Linux is not an emulator, but a compatibility layer that can run Windows applications on multiple POSIX-compliant operating systems, such as Linux, MacOS, and BSD.

It should not be confused with a virtual machine or an emulator.

Wine provides binary compatibility, support for graphics, sound interaction, as well as support for modems, networks, scanners, tablets, keyboards, and other devices.

PPSSPP - PSP Emulator.

PPSSPP lets you play PSP games in High Definition. It is fast, portable, powerful, easy-to-use, well-designed and open source graphical application implemented in C++ around the Qt toolkit and designed from the ground up to act as a PSP (PlayStation Portable) emulator.

With PPSSPP you can play PSP games a tablet, customize on-screen touch controls, use an external keyboard or controller, save and restore games no matter what the platform.

MAME - Multi-purpose Emulation Framework.

MAME's purpose is to preserve decades of software history. As electronic technology continues to rush forward, MAME prevents this important "vintage" software from being lost and forgotten. This is achieved by documenting the hardware and how it functions.

DOSBox Emulator.

DOSBox emulator is the kind of program, that emulates an IBM PC compatible computer running a DOS operating system.

Many IBM PC compatible graphics and sound cards are also emulated.

This means that original DOS programs (including PC games) are provided with an environment in which they can run correctly, even though the modern computers have dropped support for that old environment.