What level of power in a laser pointer is needed to see the laser beam?

I'm looking into buying a laser pointer, but I want one where you can see the actual laser. I want one that can go really far, but is pretty cheap. It doesn't need to sting skin or pop balloons (although that would be cool), but I'd want it to mainly be seen for a long ways away and the actual laser to be seen (like the line).

Thanks
to see a laser line you need particulate in the air, dust, fog, smoke, etc. go to a laser light show and get the idea. you can rent a smoke machine at most theatrical supply stores.