Keeping with the theme of just using a single light, I thought I'd show how to create a completely different style of photo. For this photo, I used a single flash head to create this portrait with a very different feel to it.
Here's the lighting diagram for this shot, and then let's go through what's happening here...
The basics of this shot are that I used a flash head fitted with a snoot to camera left, and a silver reflector to camera right. However, I don't actually own a snoot so I made one from black foil (search Google for "black foil photography" or "black cinefoil"), which was then wrapped around the flash head and taped into place.
Using a snoot provides me with very directional light, but also a very hard light leading to dark shadows. The light was pointed across the face of the subject, but more towards the silver reflector as I wanted some light to come back and fill in the [very] dark shadows on the camera right side of the face.
Because there is such little light spill from the snoot, there's no light hitting the wall at the back and so the background is rendered black... of course you'll need to set your shutter speed and aperture to kill any ambient light first.