I only just finished Warhammer 40,000: Space Marine last weekend and Relic is already showering me with more Ork stompah goodness thanks to the free 'Exterminatus' mode. Alas, it won't let you lay waste to an entire planet from orbit. Instead you'll just have to do it the hard and old-fashioned way, with four players cooperatively wielding their warriors of the Adeptus Astartes to purge the heretic, kill the mutant, and burn the unclean. In other words: horde mode for Spoice Mahrine! - The Videogame.
You can choose between the Tactical, Devastator, and Assault classes in two Exterminatus scenarios, which have dynamic challenges to complete and score modifiers for da extra pointy bitz on the global leaderboards. Any experience your earn counts as multiplayer experience to rank up and progress across online modes.
The free update sounds like a welcome addition for people who are not playing some other shooter game that came out today, and it should be available on PlayStation Network and Steam right now, with the Xbox Live update following shortly.