Weaponlights,
Note: I never said weaponlights offer no use at all, just no use for me, and I'm on defense. If I had to kick doors down for a living, I would have a weapon light.
I don't use a weapon light because I don't need it, and it adds weight and bulk. Here's why I don't need it:
Home defense scenario. My home is 2,600sq/ft. Aside from double pane hurricane windows whch would require smashing, there are 3 ways in. Side garage door, front door, back door. Back door is most vulnerable, but it too would need it's glass broken. If I am alerted in time, I will grab either my pistol or my AR. If AR, I won't even have time to turn on my Aimpoint (I leave it off despite the 50,000 hr battery life)...There's even an AK in my safe I can grab (safe stays open when I am home, safe is in my bedroom). I'm going to stay in the bedroom with a weapon calling the police. If they come through the door, I will empty my magazine at them. I don't need a weaponlight to aim at the door or to guarantee hits. (There's also enough ambient light from electronics that it is not a 100% pitch black scenario, although that isn't a substitute for light, I know in my environment I can direct fire at the target successfully) I won't hunt for the thug in my living room. He/they can have my electronics, that's what insurance is for. Florida law protects me in this situation if my "target identification" isn't exactly perfect. I doubt that though, because who the hell is going to physically force their way into my home by either breaking a door, window, or tearing into a lock..then proceed to go throughout my home till they get to my door? A senile person isn't going to do that. A drunk person isn't going to do that. If it is someone out of their mind due to drugs or whatnot, then they deserve to be shot because whatever the motivation (motivation is not MY problem), they are committing a a felony.
Hurricane disaster scenario. In this situation (which can happen) I must defend my property from looters. I can do this at night or during the day without a weaponlight. Again, I am on defense. I know my land, I know my house, I know my neighborhood. Depending on the condition of the home, I'll choose where in my home I will station myself. I have family in the area, and being that I live on the highest ground, they will bring their arms too and if need be, we can run shifts. People who aren't up to no good have the common sense not to go around to people's houses and start sneaking around or breaking in, especially at night.
Riot scenario: Mass outbreak of some riot/looting for w/e reason you can think of. This can happen at night or day. I'm assuming there would be mass vandalism, arson, breaking and entering, and assault and battery of anyone caught outside. These things don't happen often in neighborhoods, mostly in commercial property areas, but say it poors into my 'hood', I will be ready, and do not need a weaponlight to protect myself or my home. Fortunately, riots only run a finite amount of time. I can stay up and alert the whole time.
Those are the 3 big reasons. Now, If I were a police officer, or I put it in my head that when something goes wrong, I need to clear a room, search for a perp, or I make the decision that I will commence with an offensive move...then a weaponlight will come in handy. That I do not deny. At that point in time YOU are actively seeking ENGAGEMENT, so who cares what the light does as far as giving away your position. It will help because you'll be illuminating your target for quicker "resolution" of the situation.
The people who are defending the use of weaponlights said it themselves in this thread "if you have to clear an indoor structure in low-light." ...why would I need to clear an indoor structure? Not part of my defensive plan.