Schizoid: Available on Xbox Live Arcade

With a name like Schizoid how could you not play it.  It will cost you 800 Microsoft Points.

Cooperative gameplay is redefined in the fast-paced and unique Schizoid! Control red and blue ships, ramming them into enemies of the same color to destroy them. But be careful, because if you hit the opposite color, you will be destroyed. Quick thinking and quicker reflexes help you seize victory, but sharp teamwork provides the best chance of earning gold medals along the way. Schizoid offers more than 120 levels of challenge, playable in either single-player or co-op mode, plus the brain-melting Uberschizoid hardcore mode, in which one player controls both ships!