-ADL with Quad Gun/Lascannon (depending on the BS of the guy firing).
-A delivery system for your troops (be that a transport, deep strike, infiltrate, scouts, outflank ect)
-Plenty of scoring units. With 5/6 Eternal War missions being objective based your going to want lots of potential units to hold them!
Without knowing your codex it hard to get into specifics.
This is perfect, exactly the kind of info I'm looking for. My post is more of a general must-have type units that would be relevant to all codices. I use the BA codex, but wanna get a feel for what others feel are necessities regardless of dex.