Kamurai
Great watch, would watch again, and can recommend.
For a movie of nobodies (not true, but that's sort of what the movie feels like) and a setting of a single house, they do an amazing amount with limited resources.
Overall plot is actually a simple mystery that affects the character driven stories the entire movie. Just the idea of what people will do when they're trapped and panicked together is a great concept.
As the situation grows more dire and their sanity fades, the movie gets better and better.