Primaris Captain
Primaris Captains are going to be the analogues of Space Marine Captains and are decked in a new Terminator-esque Gravis Armor which somehow manages to be even MOAR egg-shaped than a Squat Hearthguard. Armed with a master-crafted power sword and a boltstorm gauntlet (essentially a 3-shot bolt pistol attached to a power fist) as well as 6 wounds, it'll be a tough nut to crack. But more importantly, it allows friendly units of the same chapter within 6" to re-roll any to hit rolls of 1.