I swear by my auto-on Viridian laser. Magnet switch on the laser, magnet in the holster. Draw, it lights automatically. I set elevation and windage to zero it in at around 20 feet. If I have to fire from cover and can't create a good, traditional sight picture...I simply place the dot on the target, and pull the trigger.
Yes, it could technically give away my location if I hold it on target long enough before firing. But I don't plan to have it on target that long, before firing.
That said...I hope this is all an exercise in academics and I never have to put it into practice.