Beast Warriors, released in 1990, is a side-scrolling beat 'em up for the Sega Genesis, developed and published by Sega.  Players control one of several animal warriors, each with unique abilities, fighting through hordes of enemies. The gameplay is similar to other beat 'em ups of the time, with a focus on combo attacks and power-ups.  The game featured distinctive graphic style and is generally considered a fairly solid example of the genre for the Genesis.

Beast Warriors (Japan)

BattleTech - A Game of Armored Combat (USA)