I like the gauss blaster so far, it will be interesting to see over a dozen of them that you will field from your army list. I can't wait to see your versions of the flayer and tesla weapons as well.
A question though, how will the Immortals/Eternals differ from the regular warriors? Will they be better armored perhaps? or maybe have a little bit more sentience than their warrior type brothers?
The Immortals are going to be based around the Flagellant models so they'll be a bit beefier in terms of physical build (Zombies are thin and weaker looking but the Flagellant models have some musculature to them).