What are some good XBLA games?

[Mr. Monday Morning]

Originally Posted by U-Warrior Fucking Ikaruga. A good strategy for shooters is not to think. Just react. Because most of them just throw a ton of shit at you and say "GOOD LUCK, FUCKER!". I f you put yourself in the zone, you'll do better than if you're thinking about each move. But not I karuga. Nooooooooooooooooooo. Those fuckers put shit in your way that FORCE you think, breaking you out of your trance. And you only got a split second to think of how do get past it before you are overwhelmed. Fuckers. Love this game.

I'm assuming you haven't even thought about scoring techniques yet.