Valve announced today that Left 4 Dead 2 will include a new game mode. It's called Scavenge and it's a new flavor of competitive multiplayer.

In Scavenge, a team of four Survivors must round up gas cans to refuel a generator. A timer is constantly running down and the only way to add time to the clock is to pour gas into the generator. While they try to do this, an opposing team of four Infected attacks them and attempts to destroy gas cans. The teams swap roles after one round and the squad who delivers the most cans during their turn as Survivor wins.

L4D2 will also include the three modes currently available for the first Left 4 Dead: Co-op, Versus, and Survival. There's also new weapons and Infected "bosses."