Any quality compact pistol laser will be more than up to the task. A 12ga shot gun is powerful, but the recoil impulse is slow. Compared to having a laser near the muzzle of a .40 S&W, a receiver-mounted laser on a shotgun is barely even getting used, much less punished. If your plan is to mount the laser to a rail on the top of the receiver, just make sure that you can activate it easily with your thumb.
I bought a CT Laser Saddle and it went bad in 2 days, without ever even having a round fired. The activation pads started working intermittently the first day, then not at all by day 2. I sent it back and went a completely different route: an upgraded front bead and a micro red dot sight. I know any manufacturer is bound to let a few bad units slip through QC, but when it comes to something I might count on to save the lives of my family, they don't get a second chance to make a first impression. I also refuse to buy guns (like Keltec pistols) that require extra work on a brand new gun to make them run right. If it doesn't function properly right out off the box, I'm not going to trust it to work in an emergency after it's been used for a while.