Flashlights: Necessary? Nice to have? If so, which ones and how to carry?

I've been considering either a gun-mounted light (TLR-6) or a separate flashlight to EDCWhat are your opinions? Is a flashlight of either kind helpful to have? If so, what do you carry and how do you carry it? What are some options I should look into? via /r/CCW https://ift.tt/2IZlvRb