It’d be interesting to see boss fights, where all the players team up to fight it. May be too chaotic, but it’d be fun. Perhaps they could increase the boss’s size to differentiate it more with other players.
Capture the Flag
This is a game mode idea, it consists of two teams, each team could have a fort with their flag. There are two bridges just outside of the forts that lead to the middle, which will be a medium sized circle, where players fight, and throw each other out. The point is to make your way to the other teams fort and steal their flag. You have to grab the flag first a period of time, just like infecting players in infection mode to grab it. The flag could be on your back, to regain the flag, the other team has to knock out the player with the flag. You win the game once you have your own flag and the other team’s flag inside of your team’s fort, on top of some pedestals or something.