I'm finding L4D to have marvelous propensity for gameplay-created narrative. Three examples:
My very first time playing and it's on No Mercy. We get to the final wait for the chopper and I don't know what to expect. We battle off the hordes but things get to going badly just as the chopper's landing. I then realize I'm the only one still standing and madly run to the chopper, desperately meleeing zombies out of my way. I make it as the sole survivor and feel awesome. Then the "credits" start to roll and I see "In memory of" and I'm all, did someone at Valve die during making this or what? Then it scrolls up with the names of the other 3 players and I have a good lol.
It's the end of Death Toll and things are again going badly. One person's dead, one person's on the boat, I'm running across the dock nearly to the boat, and the last person's still on land. A couple steps away from safety, I turn around to see the straggler Zoey go down to a swarm of Infected, pistols still blasting in defiance. I'm low on health but I figure I should be able to manage a rescue since it's just some normal zombies. I run back to the incapped Zoey and promptly get my legs shot, downing me. The lone boatman sails off...
It's Chapter 4 of Death Toll, which always seems hard. Three of us are alive, all with 1 HP. We round a corner and see the safe house door. No zombies are in sight. Just as the dude in the lead gets to the door, a Tank hurtles out from the alley to the right, instantly killing him. The other survivor and I scream and run, but we both get knocked down. :(