I found a great Shmup last night that even has a version for the lowly Mac users
Gridrunner++ (llamasoft) is a psychedelic thrill ride through the bowels of computer generated euphoria.
it doesn't get much better than this if you're a fan of the shmup genre
Oh and as you're playing large sheep heads fall from the sky which you must grab as power ups.
This is a Really great game that is avail. for PC or Mac in Demo form and Im gonna go back and buy the full version!
It appears theres even a version for Mobile devices!