I prefer to carry a handheld light that protrudes past my palm when I hold it in the typical hammer fist grip. There are two reasons for this: first, it is easier to point and light things up with the Bezel unobstructed by the hand. Second, I like having the ability to strike with the light.
Hitting somebody with the bezel of a good light imparts impact on an order of magnitude greater than hitting them with your bare hand in a hammer fist strike. The light can also be a game changer when used as a pocket stick sort of tool when on the ground and in the clinch. Combatives guru Kelly McCann teaches how to deploy such a tool, be it a pocket stick, kubaton, tactical pen, or light, when on the ground, as it proves quite effective at getting someone to react and get off of you. After training with him I consider this another benefit of a good handheld light. Digging a hard object into the ribs of an aggressor gets their attention far easier than anything that can be done with bare hands. I like the light in this capacity as it is very easy to get to if clipped to a hip or back pocket, when on the ground. Also, being able to break glass with a striking tool that is always on your person is a significant bonus.
Still, there is no magic in the light as a striking tool. While it can greatly enhance the power and effectiveness of your strikes, you need to have the hand skills to land the strikes to begin with. If you have those skills, then the light can be a force multiplier for certain scenarios as an impact tool.
See the explanation of the light as an impact tool: