In Paranormal Activity 4, Katie and/or Toby attempt to asphyxiate Alex by trapping her in the garage and leaving the (locked) car running. After many unsuccessful attempts to open the doors or cry for help, Alex grabs her father's golf clubs, breaks into the car, and instead of simply stopping the engine, she guns it in reverse to smash through the door and into clean air. More than one audience has cheered and applauded at this 15 year-old's intelligent response.
The boyfriend is a walking, talking crowning moment of awesome. He points out how the Kinect detects movement, he helps the family document what happens in their home, and furthermore, he's the smartest in the film with the funniest lines too. Too bad he dies in the climax.
The exorcism scene in #2 is the closest thing to an intense climax that the series has gotten.
A meta-example: #1 was made with a measly budget of $15,000. The box office total? $193,355,800. If that doesn't seem like much compared to some other films, then think about this: the film pulled in a little over 12,890 times the money it took to make the film.
The gangbangers fighting the witches in The Marked Ones.
The Extermination Ritual in Ghost Dimension. Father Todd and the family draw as seal of Solomon and circles of salt in the living room. Then they use Leila as bait to draw out Toby and trap him in the circle, after which they smother him in beach towels soaked in holy water and chant the ritual to banish him. The whole sequence is seen through the night vision setting of the spirit camera and is spectacular, even more so for being the only instance in the whole series where the protagonists put up any kind of successful fight against the demon.