The Sacrifice

The Sacrifice is a three-chapter DLC for both Left 4 Dead and Left 4 Dead 2, it was released on October 5th, 2010. The Sacrifice is the 6th and final campaign of Left 4 Dead.

The Sacrifice takes place after Blood Harvest, and is considered to be the prologue to The Passing, as both campaigns are connected to each other. The DLC is free for PC players, while for Xbox 360 players, it comes in two separate packages on Xbox Live (one for Left 4 Dead and one for Left 4 Dead 2), and costs 560 Microsoft Points for each one.

The campaign's name comes with the obvious interpretation that one of the Survivors has to sacrifice themselves in order to enable the survival of the team. Canonically, Bill is the one who makes this choice, as seen by his unfortunate appearance in The Passing's finale inside a generator room, as well as the comic.

The tagline, "It's your funeral," refers to the idiom "it's your funeral", basically meaning someone may have made a bad choice, and if they follow up on it, they will have to endure the direct consequences regarding that choice. During the campaign, the team will pass by numerous boats and Francis constantly suggests for the team to take any of them, but Bill refuses to listen to him and insists into finding a sail boat. Later, at the beginning of The Barge, Francis notes that they could have used one of those boats to move around and find a sail boat safely. Bill admits that Francis is right, but obsessed to find a sail boat right away, he still refuses to head back even when they find the raised bridge. Had the team headed back, the titular sacrifice could have been avoided.

Walkthrough

 * 1) The Docks
 * 2) The Barge
 * 3) Port Finale

Both Left 4 Dead and Left 4 Dead 2

 * The Sacrifice campaign.
 * New dialogue for all the original Survivors, including community ones for Bill.
 * A new item "Explosive Barrel", which acts like a propane tank and a gas can. It can be triggered by flames and gunfire, as well as being moved by melee shoving, but it is not portable.

Only for Left 4 Dead

 * The Heavy Machine Gun that was previously only available in Left 4 Dead 2 is added. While it only appears in Port Finale at an equivalent location to its placement in The Port of Left 4 Dead 2 in official content, it can also now be used freely for the design of community campaigns in Left 4 Dead.

Only for Left 4 Dead 2

 * A port of No Mercy which includes usage of the original Left 4 Dead Survivors.
 * Five New Mutations: Taaannnkk!!, Hunting Party, Lone Gunman, Bleed Out Versus and Healing Gnome (only for users who have bought or own The Passing DLC).
 * New dialogue about the Left 4 Dead 2 Special Infected for Bill.
 * The CEDA Worker Infected and the Worker Infected also appear in this campaign and in No Mercy.

Achievements
Unlike other campaigns, The Sacrifice's Achievements can be obtained separately on both Left 4 Dead and Left 4 Dead 2. Two of the Achievements, SUPREME SACRIFICE and KILL BILL, are only obtained by the player who sacrifices themselves in Left 4 Dead, while in Left 4 Dead 2, it counts for the whole team.