Dungeons & Dragons: Chronicles of Mystara is a classic arcade 2D sidecrolling beat 'em up that costs $14.99.
Code of Princess is a 2D hack and slash game with some RPG mechanics. Originally designed for the Nintendo 3DS and ported to PC.
Fan game based on Streets of Rage franchise (from Sega Mega Drive / Genesis). Includes characters, music and locations from all games, and also new content.
Castle Crashers is a 2D sidescrolling co-op action beat 'em up game.
Ascendant is a 2D side scrolling beat 'em up game for PC that utilizes many roguelike features such as randomly generated levels.
Shank 2 is a continuation in the Shank series that features classic side scrolling brawling action. It costs $9.99.