Kasr'kin Squad. Kasr'kin are veteran Guardsmen, with better equipment (Carapace Armor and Hellguns, sergeant carries a Bolter, three troopers carry special weapons - two plasma guns, one melta). DoW conflicts with canon here, as kasr'kin are exclusive to Cadian regiments (This picture shows Valhallan 24th). There are Stormtroopers that are similarly armed, but unlike kasr'kin Stormies are trained in military orphanages aka Schola Progenium, like Sororitas or Commissars.
And by the way, there's one of the latter there too, and the quote from the title is from his voiceover (It even was carried over to DoW II Retribution Lord Commissars). Their very purpose is to inspire the flak out of Guardsmen, and enforce discipline, among troopers and officer staff alike (by summary execution shall the need arise). Hence the pompous hat, black stormcoat and a loud and flashy bolt pistol along with a power sword (some prefer laspistol for reliable ammunition (Ciaphas Cain) or plasma pistol for ability to hurt even light vehicles (Viktor Hark), and grab a power fist for close combat).