Today I found out that when the body is asleep and something traumatic like a heart attack occurs the person dreaming has a lucid nightmare. For example if someone were to commit suicide with pills that took them a minute to pass out and 30 to die, those 29 minutes before death would be a lucid nightmare as the body responds to the shock.
What if someone where to make a game where the player is basically in that lucid nightmare? As the game progressed things would only get more bleary and ethereal till the player finally died and it was revealed it was a suicide the entire time. There could be a number of meaningful interactions that would characterize the player's life, fears and dreams in a number of very scary ways. Perhaps a mechanic where you're running from inevitable death or with conversation branches with NPCs in very small areas of the player's life. It can also be possible that the mechanic changes with each of these small areas where a new objective must be reached.