I enjoy going to the theater to hear the guy next to me eating popcorn with his mouth open and maximum mandibular crunch. Also, I do enjoy the woman behind me that with her constant non-stop vocal reactions to everything onscreen (anything mildly sad --> "awww"; anything vaguely surprising --> "oooh"; ...).

Other highlights include the super bright EXIT signs flanking both sides of the screen -- helps me get immersed in the scene. The occasional loud bass rumble from the action movie playing one theater over also helps.