For the final rollout of Left 4 Dead 2 goodness before launch, Valve announced the new Scavenge mode. This 4 v. 4 mode pits survivors against infected and not in the way you've come to expect. Four survivors must retrieve gas cans around the map to power a central generator. Each can that is poured into the generator buys 20 seconds of time on the clock which counts down to the survivors demise from 120 seconds. The catch? You can't take damage when filling the generator and the gas cans are spread so widely throughout the surrounding area that it takes an impressive feat of skill and teamwork to get all 16.