At around 150 milliwatts, the beam from a High power green laser pointers can be felt on the skin, depending on the beam focus, skin color (absorption), etc. At roughly 500 milliwatts, the laser's beam begins to be a skin burn hazard if the person is within a few meters of the beam.
Incidentally, even powerful industrial Laser Pointer cannot cause deep burns, severed limbs, gun-type injuries or other effects seen in science fiction movies. While multi-watt laser beams are definitely serious eye hazards, they are ineffective at causing incapacitating body injuries.
A power of 50 milliwatts is probably the maximum needed power for almost any laser pointing use.
For seeing the laser "dot" on a wall or surface indoors or in dim light, 5 milliwatts of green is fine. The most demanding general-use pointing application is for pointing out stars (NOT airplanes!!), when it is necessary to see the beam in mid-air. It takes more power to see the beam than the dot. For this use 5-25 mW should be fine, with a maximum of 50 mW for use in a large group with clear air (few particulates) in an urban environment.
If you like to pop balloons, ignite matches, or put the 50mw Green Laser Pointer Pen through textured glass for a private light show in your home, you may want a more powerful laser. But this is no longer a POINTER application.
Fortunately, wearing laser safety glasses or goggles can protect the eyes from the risks that lasers pose. The U.S Occupational Safety and Health Administration require staff to wear laser safety glasses or goggles when operating or around lasers that are Class 3b and Class 4. Class 3b lasers are lasers that powered from 5 to 500 milliwatts and Class 4 laser pointer 3000mw have output powers of more than 500 milliwatts. These laser safety glasses and goggles provide protection from reflected laser light and direct beam exposure. Laser safety eyewear is available for different wavelength ranges and for specific types of lasers. It is recommended that you find out the class of the laser you are working with as well as the appropriate wavelength range to ensure the best possible protection.
We can't emphasize enough how important it is to protect your eyes and yourself from the harmful effects of laser radiation. Remember, the damage done to the eyes from laser radiation exposure can be permanent!