Same idea I pitched when a similar thread was made:
Spoiler below!
You're a guy on a Haunted House amusement ride, then things go wrong.
Imagine this; It starts up with the player walking onto the platform, walking through the turn-stile, loading into the single-cart coaster and with a retching jerk, the cart begins to move. The beginning would start off looking REALLY cheesy with cardboard cut-outs popping out at you, stupid eerie music and other things just generally breaking down. Then the ride stops, the music warps and fades off. The operator comes over an intercom, explaining the situation and then, you see it come around the corner, shambling towards, the foreboding, invincible evil force shrouded in darkness.
Then, BLAM! A part of the ride above you breaks off, and comes crashing down between you and the aggressor forming a large hole in the shotty ride, sloping the rail and slowly moving your cart to where you and the aggressor fell into the darkness.
The player awakens to find himself inside the broken down ride and must find his/her way out.
The aggressor would have to be something different from the monsters of Amnesia, maybe a mass murderer or maybe some psycho in a ragged mascot body suit.