In my experience with lights on shotguns, the mount is just as critical as the weapon light itself.
I have used cheap (in this instance meaning inferior) mounts and they tend to slide and move around under recoil despite how tight you clamp it to the tube.
The Elzetta mount is the only one that I have personal experience with that doesn't do that.
It's more expensive than many other mounts, but it works.
And as for a light, I'm using one that isn't even technically a weapon light. It's a ray-o-vac "indestructible" AA battery light with a few wraps of black tape around it so the mount will clamp down on it.
While this may sound very jerry-rigged, and I assume it probably is, it has never failed me, even like many others.
The light itself is an LED and has 2 brightness settings. So, when I use the light, I make sure the last time that I click the tailcap that it's on the low setting so when I do use it, it will be on the higher setting.
It has a clicky tail cap on/off switch so if I want it on, it's on. And if I want to use it as a momentary switch, I just don't click it and depress it down all the way.
This isn't the best photo of it, but does show the mount and the light.
And since I am a fan of testing my gear out properly and in the manner of which it would be used, the night time shooting of the gun above is at the end of this video