Light your performers from below to create a creepy zombie effect, with stark white lights against total darkness. The resulting shadows are unsettling and don't even require makeup to scare.
For extremely low budgets, have the actors simply hold flashlights below their faces.
Shine high-contrast lights on the performers from above to cast an otherworldly or angelic effect.
White spotlights used in this way can be a dramatic way to isolate the performers, or to enhance a sense of loneliness or sadness. Overhead lighting in softer yellows will meanwhile give a more 'heavenly' or angelic feel.
Create the effect of a "flash" of lightning through the simple, swift flash of all white lights to full, then off. For a stormy nighttime feel, use ellipsoidal lights without gels, keeping the light 'white' and directed from before and above the stage (leaving the back dark for contrast).
Use a tiny laser or reflective hand mirror to simulate a fairy or firefly in the action. The hand mirror can be wielded by the performer and hidden in the palm of the hand, or used from slightly offstage, directing the reflected glimmer of light back against the stage wall.
Cover your lights with red gels in order to create an impression of anything from Hell to a volcano, furnace or other fiery location.
Red lights can also be an effective way to imply a sudden bloody outcome, especially if used against white costumes or set pieces.
Place blue-colored gels before your lights to create the effect of moonlight or deep evening, or even an underwater environment.
Use bright yellow gels to create the impression of a beautiful sunny day. For an extended scene, subtly bring up some orange-hued lights as well to simulate the stretch of afternoon into sunset.
Signal the mood of the production through an overall lighting theme in color and intensity. Dramas, for instance, are typically darker, with spots of higher contrast, adding an element of isolation or even impending tragedy to the look and feel.
Musicals and comedies, on the other hand, tend to be brightly lit, and with pastel color palettes, low contrasts and sunny colors.
Place a flickering silk flame light onstage to achieve a campfire effect, adding to the effect if needed by partially covering or encircling the light with sticks of wood or fake wood. Silk flame lights are surprisingly inexpensive and realistic in appearance.
As an alternative "do-it-yourself" approach to an onstage campfire, hide a bundled string of flickering red lights under a tee-pee of fire-resistant 'sticks'.
Use a strobe light to elongate a moment or to simulate slow-motion at an important moment.
Simulate water through the use of an actual water-effect LED light, as the outcome is both realistic and the equipment is now extremely cost effective.
For a more low-tech approach, reflect cool blue lights off of lightly reflective material on the floor in order to simulate a pond or lake.
Simulate a futuristic or alien instrument panel by hiding strings of colored lights within the desk or set piece, so that the lights flicker up into the actors' faces as they bend or work over the panel.
For 'radar' panels, hide an LED light that is green for a similar effect.
Hang a string of pinpoint LED lights high against a black background for a beautiful starry-sky effect.
To achieve a similar effect on even the lowest of budgets, punch tiny holes of varying sizes and distances in a large length of heavy black material, then hang high against the back stage wall. Complete the effect by lighting from behind with a fairly white, harsh light--and presto, you've got stars!