I've been playing games for a long time so it's not just every day that I see a game, know nothing about it, and yet am entirely sold. I have found that game. It is called Music GunGun! and it is everything you could possibly imagine with a title like that and o'so much more. Similar to Elite Beat Agents and even Guitar Hero, the players ability to shoot on target completes the melody.

Music GunGun! made its debut earlier this year at the Amusement Machine Show. The game plays like you would imagine. Using gun shaped controllers you shoot targets to the in sync with a song. The enemies in this game are adorable circular creatures that allow you make music along with the game. And the adorable doesn't end there, since most the sites are in Japanese I'm not sure why, but there seems to be plenty of kittens in this game too.
According to Joystiq the game plays more like your typical rhythm game more so than a shooter. And unlike both genres of games, towards the middle of a song there is often a "boss battle" where the mission is no longer to shoot to a beat but shoot to kill.

The game can be played with up two people with competive and cooperative modes.. Sadly it seems that all seven arcades left in American can't afford to pay the price to import the game over here. It has been playable in Japanese arcades since July.
Source
Images