If you like side-scrolling beat-em-ups and have a friend or three to that can sit and play with you I would totally recommend
Scott Pilgrim vs. The World: The Game
It's 800 Microsoft points. I found it to be pretty fun, and I loved the soundtrack. However, I do emphasize that this game is most fun when played with some friends.
Another game I would suggest would be the original Toy Soldiers. It's 800 Microsoft points I think and it's a pretty fun take on the "Tower Defense" genre allowing direct control of defensive units, and I believe it lets you send out offensive troops as well. (Don't quote me on that last bit though

)
Hope you find a game worthy of your points!