I'm having trouble trying to count the number of people I know who've had trouble with internal guide rod lasers. In any case it's quite a few. As a matter of fact, years ago, it was a fellow at Glock Technical Support who, first, made me aware of the problem.
Pistol lasers are great training devices; not sure whether or not I'd recommend one for SD combat, though. The aiming technique is different; and a fair amount of practice is required before a user becomes instinctively good with using one.
What's the best pistol laser? I'm going to go with Crimson Trace's grip-mounted unit.
I have the Crimson Trace grip mounted lasers.
I don't like a weapon mounted light because you have to point your barrel at whatever you want to see. I carry a Streamlight Strion led (160 lumens, 3 light levels and strobe, with rechargeable battery) every day. What would you feel like if you were clearing your house when your wife heard a noise and you brought your weapon mounted light around a corner to see the darkened hallway and you lit up your toddler. To me that is not worth having the light on the weapon. Also I have read that the light is what someone would aim at if there was someone firing at you and you can hold a flashlight at arms length.
Just my 2 cents.