I liked Telepath and silicoid - you skip all food and ground-combat skills, since you take over planets with your mind! Better than the Psilon who get all tech branches - you don't even need half of them! And can do industrial development on all planets (no wasted population making food)
Btw what I loved in Moo2 was taking planets with their population, you didn't just wipe them out, but assimilated them in your empire, and could use those colonists to settle inhospitable planets.
