My dept issues 870's w/ surefires. I carry a personal 590 and was going to put a surfire on it. The prob was that you would not be able to use a sling on the gun due to the location of the light. So I decided against it. I ordered a M 1907 Sling today from Turner Saddlery ($51.95 including shipping) I have found that a good sling on a shotgun is very useful. The light would be to, but I don't want anything on my guns that runs on batteries.
When guns are outlawed only outlaws will have guns.