Also, just from experience, I've seen green lasers ranging from 5-25 mW in day and night, and they are both PLENTY bright and emit a solid stream of light that can be seen from any angle. During the day, evena 5mW laser is clearly visible in the broad sunlight.
If it comes to intimidation, i think a 5mW is still gonna work. If you notice with lasers, if its being pointed near you it appears VERY bright (you see the beam and the emissions from the actual laser diode). If you want the target to know you got a bead on him, a 5mW laser is gonna do a good job. I mean, we're talking about marginal returns here, spending hundreds on a laser is not a good investment if you can get somewhat the same results with 60-70 bucks.
if you really want to spend that much, by a surefire (i think thats the company) green laser. They are one of the only green lasers specifically designed to be mounted on a rifle or shotgun. They are pricey though, like 500 bucks or something.