I think this horror movie came out in the early 90s.
A group of people in their early 20s stay in a house, believing they will be filmed as a reality TV show. Then, suddenly, they are locked inside the house and are slowly killed one by one in a gruesome manner.
I remember that the first person is killed by an axe shaped device that shoots out of an oven. Then a circular saw shooting up from the ground.
Later, another person is killed and their head ends up on a platter decorated as a disco ball? (If my memory serves me correctly).
Toward the end of the movie, the main character (female) has a discussion with herself in the mirror. She pulls out a switchblade, and caresses it, and alludes that she was behind the terror.
At one point one of the characters says 'How about a nice tall glass of shut the hell up' (unfortunately its not dawn of the dead).