One Must Fall 2097 is one of the overlooked old classics. Deep down, it's a 2D fighting game; there are however differences that give a nice touch to the cliche'd genre. Instead of fighters, you control giant robots who will greatly vary in every aspect; you can also pick your own pilot, which will also determine how your 'bot performs in action, giving the game a huge replay value. Replaying the singleplayer with different pilots will unveil different parts of the overall story, and naturally everyone gets their own ending. In addition, there is a Tournament mode, where you can train your pilot and build your own robot, getting customizations not available in normal singleplay and the secret boss robot as well. Further difference from the genre is the interactive terrain; maps almost always contain dangers which can easily turn the tide of battles. All in all, it's a highly recommendable game, and highly time consuming as well =)
You can download One Must Fall 2097 here.