Some of the starwars games had side games that were Co-op. Basically you and a bunch of friends were put in an areana to face unending waves of enemies.
I could see a mechanic where players are given "tricks". basically abilities that modify the game whenever a player activates one: Enemies counter tracking missiles, players shields slowly drained(soft time limit), and other similar mechanics that affect ALL players.
So all players are rewarded for surviving and similar. However if a player dies when one of your tricks are active you get extra bonuses.
Could see this brief mechanic going well with a horror game. You know you have allies who want larger rewards by advancing further, but at the same time you know those same allies want you dead from time to time with expected help just not coming.
Was that a really thing or something you came up with?