Adaptation Distillation: The film fleshes out the background for the actual characters, but the game does a better job of conveying a horror atmosphere (what with the constant tension of not letting your characters die and the emphasis on teamwork).
While some combinations have a logic (e.g., a camera flash on bats or ghosts, a mallet that shatters evil mirrors), others are pretty obscure (e.g., using a small lighter on hordes of bloodthirsty worms).
Achilles' Heel: Many enemies will take more damage if attacked with specific weapons or objects.
Accidental Murder: Lady Mamiya accidentally killed her baby by turning on the furnace when he was playing inside it.
Absurdly Low Level Cap: The level cap (made more difficult to figure out due to the fact that you can't see your own level) of 20 can be comfortably achieved a little over halfway into the game.
The video game version of Sweet Home includes the following tropes: