Laser sights

They can be effective, once dialed-in, but are'nt exactly a replacement for sights and /or a light. They are good for night/poor lighting use, to get "on target" quickly vs. trying to get even a rough sight picture in poor/no lighting.But, this all assumes you being able to adequately SEE the target, to begin with...
Have mounted and used one on my 870, with good effect, to get roughly where I need to shoot, but havent yet found one to try on my .45, so..
I find that, with shotguns, they can come in very handy in low/no lighting situations-for shotguns that have only a bead front-sight, when stock.

In day/lighted situations, they arent very useful, most of the time.

I've also tried those fiber-optic replacement sights, as well. Useless, really, unless you've kept the shotgun in a lighted area for a while, prior to use, which is unlikely, unless you sleep with the lights on at night... (assuming shotgun is kept near the bed for immediate access, when needed).

I use a Viridian C5L with A Viridian Tac Loc holster.

I use the Viridian X5L it is larger than the C5L, but to me the extra lumins on the strobe are what I was looking for in a home defense laser pistol combo. I love the viridian lasers, because even in the noon day sun you can still see the beam. Although very distracting to other shooters, sighting the laser is very critical to accuracy, no matter what type.