Strobe lights, blacklights and other special effects. You can also achieve some very interesting lighting effects through the use of strobe lighting. This effect can be very easily overused, but judicious usage can add tension and drama to a scene. Very often a strobe light is employed at moments of powerful action, such as the final death scene of a villain or the crucifixion scene in a church play. The audience only gets bits and pieces of information, and the action is slowed down considerably.
Strobe lights are usually quite affordable, or can be borrowed from any number of people.
Used in conjunction with a smoke machine or dry ice, strobe lighting can be highly effective in haunted houses. Another special effect light that can be very impressive in small doses is the blacklight. Angels or other supernatural forces can appear to glow with the use of a blacklight and white clothing. Floodlights can also be easily rigged with blacklights, giving a new element in night scenes or to emphasize certain pieces of flourescent scenery. Again, less can be more.