Frequent visitors of the MSX Resource Center already knew the preview version of Marison's Cosmic Battle. Although the game has not been finished as of yet, a new version has been submitted as an entry to the MSXdev'05 competition.
Cosmic Battle is a nice shoot'em-up for MSX1. The currently released alpha version (a 32kB ROM file) already looks very impressive and certainly is worth downloading and playing.
Relevant link: MSXdev'05 status page