Silhouette Mirage is a very enjoyable boss rush-style game that marries shmup & beat em up mechanics with an early version of Ikaruga's polarity switching system.
I've gotten many friends to play this game via emulation, but I think it'd be awesome to have Silhouette Mirage re-released on GOG to be enjoyed by more folks. It'd be best to have the release based off the Japanese Sega Saturn original with the extras bosses of the Playstation version.