There hasn't really been a thread on this game, which I think deserves a mention as it is part of the UGSF timeline and contains Galaxian^3 stuff.
Star Ixiom is a PS1 game, it only came out in Japan and Europe (much like G^3's port) and it's a sort of evolution of the old Namco game Star Luster except it involves the whole of UGSF and multiple UGSF "universes", specifically Galaga, Galaxian, Gaplus, Bosconian, Starblade, Star Luster and of course G^3. The Dragoon J2 and Geo Sword are selectable ships and enemies from G^3 and Starblade make appearances alongside old Galaxian/Galaga/Bosconian enemies and battleships. Zolgear even makes an appearance!http://www.youtube.com/watch?v=6eM_GqBnq-s
This is the intro video, you can see the Geo Sword in action along with the Gaia Ʃ from Star Luster and the Galaxip from Galaxian. The game itself seems to be a bit rough but it has some nifty music (including an orchestral version of the Galaga music!) and the ships are rendered quite nicely.