I remember Cosmic Pirate as a fast and open-ended multidirectional shooter with huge boss fights. A neat feature was the Virtual Reality training mode, where all the graphics looked like wireframes (although it probably just was a different set of sprites). Also, the game had one of the catchiest title themes, by David Whittaker.
Screenshots marked with 🍒 are created by syltefar and are considered public domain, free to use for anything. If you want to, you can note where you found it and link to this page.