Fire Lords

Space Marines that have flaming tattoos, replace their teeth with flints, and breath fire.

Yes. They breathe. MOTHERFUCKING. FIRE.

Possibly Matt Ward's second favourite chapter, since he's put them in every codex that he has written except Codex: Blood Angels. This makes them slightly less badass, although the least awesome thing that they've done thus far is taking credit for the work of the Grey Knights.