I have Godox X Pro flash remote control transmitters for my cameras. In the neck of these transmitters is a laser head behind a red plastic window in the transmitter case that I can turn on when trying to take photos in low light, and will project a cross hatch laser beam of light on the subject during the auto focusing step of my cameras. It's only lit during the auto focusing sequence and turns off automatically when the auto focus is complete. When I press the shutter trigger button the rest of the way, the laser is off and the shot is in perfect focus.
Back in my very early days of digital photography this feature wasn't available. To get the camera to focus automatically in low light conditions it was quite a challenge. I came up with an idea to use a laser gunsight and modified one so I could attach it to a cold shoe on the camera. I could turn this laser on and the red dot on my subject/model would let the camera focus perfectly. I learned quickly to explain and demonstrate the laser to those involved, because the first time that I turned it on, everyone hit the floor, thinking that I was pointing a gun at them. After the explanation, there was no problem with using it. Since it was always on during the shot there was a red dot in the photos taken, but it was easy to remove this in Photoshop during post. Fast forward 23 years and it's now an automatic feature in flash control transmitters and called "Focus Assist" and it's only on briefly during the auto focus function of the camera, so the red dot removal via Photoshop is no longer needed. The cross hatch pattern doesn't scare anyone like the single red dot did either, and it's on so briefly that many are not even sure that they saw it. I can manually turn this laser on or off via a switch on the side of the flash transmitter, but usually just leave the switch on.
While cleaning and reorganizing my camera bags last year, I rediscovered this gunsight laser unit in the bottom of one of the pockets of one of my camera bags. I was amazed that it still worked, I had forgotten about it years ago. It went on the shelf with my no longer used cameras because I doubt that I'll ever need to use it again,
Charley