If you want a sick ass shooter check out Reflex. If your a fan of Ikaruga type game play then you'll enjoy this. The graphics aren't of those 3D type games with super flashy stuff but hey this is great for an arcade shooter and if your a fan of arcade shooters then this game is for you. Its only one player but these are the sort of games where you don't always need a 2nd player.
If you like what you see you can buy the game at: http://www.desura.com/games/reflex
You can also try a trial at: http://www.siterskain.com/reflex/download.htm