Here is an example of beams using a trans map and ambient color.

The only other method that I can think of to exclude an item from a light, is to use a mask plugged into the lights Intensity node. I tried that once, it worked to some degree, but not as well as I had hoped. To make the mask I set the Background Color to white, then set the Foreground Color to black, then hid everything except the item I wanted to exclude. Then set the Display style to Silhouette. Then I did a preview render through the shadow cam of the light I wanted to exclude. This gave me the black and white image for the mask, which I then plugged into the Intensity node of the light.