I carry a Surefire LX2 Lumamax daily that can be utilized as a weapon when no better options are allowed (i.e. airports, federal buildings, schools). Mine has been part of my EDC for 7 years now and is still going strong.
The Surefire Peacekeper riding on my belt as I type this has a gently scalloped (they call it "crenullated") bezel around the lens that serves as a glass break and self-defense weapon.
I hope to never use it for either, but it's nice to have and in no way affects its carrying comfort.
I am not sure I am strong enough anymore to swing a 6D cell maglight. Well maybe one swing but it better hit something. I used to carry a 5 cell around the summer I worked as a security guard almost 25 years ago. Not sure that old light would fit in my pocket very well.
I'm a fan of carrying a high-intensity compact flashlight every day. There are plenty of utility reasons, and it makes a great defense tool for non-permissive locations.
Many want to make things more complicated than they need to be. The use of a flashlight for self-defense is no different than any other impact weapon or improvised weapon that is used as an impact tool. Forget about the flashy stuff or the locks, take downs, and throws as shown in the intro to that video. Instead focus on gross-motor skills that can be used under the stress of a real assault- namely- hit hard, fast, and repeatedly until the threat ceases. The skills employed with a small flashlight should be equally applicable to a ballpoint pen, felt-tip marker (Super Sharpie),TV remote, pocket stick, steel or aluminum water bottle, etc. If you have a basic understanding of empty-hand skills then it's a minor issue to transition to impact weapons. While I teach classes on the use of flashlights and improvised weapons you really don't need a class unless you lack fundamental empty-hand skills.