M.U.G.E.N.: The Freeware Fighting Game Engine for Custom Creations

M.U.G.E.N. (which stands for 'Mugen Ultimate Game Engine') is a freeware 2D fighting game engine designed by Elecbyte. It allows users to create their own fighting game characters, stages, and movesets using a variety of pre-existing sprites and animations. The engine is highly customizable and has been used to create a wide variety of games, ranging from original creations to parodies and crossovers featuring characters from various media franchises.