The following Left 4 Dead 3 game play idea was submitted by top contributor, XenuLies.

Another idea for a new game mode would be one that brings an ultimate competitive multiplayer experience, I guess we should just call it Ultra-Scavenge. It would be the biggest mode yet, holding up to 16 players. It would center around 2 teams, red & blue, each team having 4 survivors and 4 infected. There would be 2 “bases” (saferoom-type areas), each with a generator for that team, and a central point where many gas cans are located. The map for this would be roughly smaller than a whole chapter, but bigger than an ordinary scavenge map. It would be divided into 3 parts, 1 for each teams base and 1 for the middle section (which would be much larger).

The main goal would be to have your team’s collect cans as your team’s infected try to stop the other team. Cans are free to grab when they are in the middle section, survivors cannot enter the enemy teams section to steal cans back, but your teams infected can enter to kill them. Cans would continuously spawn in groups of 4 (to prevent teams from collecting several in mass). It will not end until either one team runs out of time or wipes. When a survivor dies, they begin to spawn as more of your teams infected, (It would go from 4 survivors-4 infected to 1 survivor-7 infected).

The survivors of each team could be any 4 of the 12 available (4 from each game), allowing players (if they started in the lobby) to play as whoever their favorite survivor is, forming a “dream-team” with their friends. Each survivor would also be re-skinned slightly to suit their team.
For example: If the blue team were to be Zoey, Ellis, Bill, and Coach, then it would give Zoey a blue jacket, Ellis a blue shirt (and hat), Bill a blue… you see where I’m going with this. The infected would also wear clothing colored accordingly.

An alternative version to this mode could be a capture the flag type mode, where each team would need to raid the others base for the cans.