Left 4 Dead's forthcoming "Survival" mode. If you'd asked, we would have told you that you'd probably be shooting a lot of zombies for a while and then later, they'd kill you. But it is helpful to have IGN to support our theories with their hands-on impressions and the video we've put right after the break.
Apparently, Survival is designed for quicker play, with matches rarely going longer than 10 minutes (and by rarely, we mean never: Valve [the people who made the thing] have only barely been able to break nine minutes). Ironic, as nine minutes is our personal record for ... actually, never mind.