I do the flashlight thing.  I create a hollow cone or cylinder composed of a mirrored material.  I add a point light at low intensity, and a spot light with the right power and width.

If you get them all sorted out and set in the right location within the cone or cylinder the light shows only in one direction.  The cylinder is better for a more confined beam.  

Included is a sample from an idea I used in one of the underwater scenes if did previously.

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