Fire Lords

Space Marines that have flaming tattoos, replace their teeth with flints, put flamers on Land Raiders (they actually invented the Land Raider Redeemer by replacing the Crusader's Hurricane Bolters with Flamestorm Cannons) and breathe fire.

Yes. They breathe. MOTHERFUCKING. FIRE.

Possibly Matt Ward's second favourite chapter (edged out by the Ultramarines, of course), 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.

Did we mention that they breathe fire?