One of the Blog Bash door prizes was this Insight X2L laser/light combo.
I’ve never used a gun mounted light, but I like this X2. It fits on the accessory rail of my XD and it’s small and light enough that it doesn’t alter the balance perceptibly.
The only negative that I’ve seen with it so far is that there is no way to use the laser without the light also being on. I’m not sure what the thinking behind that is, but I’m sure someone knows. (yes, you can remove the light bulb and use the laser without the light.)