Let's focus on the Imperial Knight for a moment. This huge walker is the biggest unit Relic has ever made. It has gatling cannons for arms and you can target missile bombardments from its back-mounted rocket launcher. Sometimes, when it gets very grumpy, it overheats and starts spewing fire out of its exhaust pipes. During this phase the gatling cannons glow white hot, the unit does more damage, and its bombardments create additional pools of burning flame on impact. It's ace.
Elite units like the Knight have special abilities, bringing some of Dawn of War 2's tactical micromanagement into Dawn of War 3. The knight has a sweeping gatling cannon attack that can deal massive damage to a forward arc, and the bombardment missiles can be individually placed, allowing you to scatter damage across the enemy line or focus in on one high-value target.