What can a 1MW military green beam lazer pen do?

If its available on amazon it won't be able to ignite things or bob balloons. Those are laboratory grade lasers. You can basically do the same thing as any laser pointer: make your cat chase it

I use mine in my astronomy - on all but the very driest night, it can project a visible line up into the night sky, so I can point to stars, planets and constellations when I'm giving friends and students a 'tour of the sky'. I can also use it to align a telescope very quickly; I just hold it to the side of the tube, then point the 'ray' at whatever part of the sky I want to look at! Warning - if you're pointing your laser into the night sky, don't be tempted to point at aircraft - it's dangerous - an illegal, you can get sent to gaol! It also feels a little bit like wielding a light sabre!

That wont be able to do anything, go on eBay and get one of the military ones from China, i did. It pops black balloons :). They are listed as 1MW, but that's only because they can't sell a laser higher than 5MW, so it's just a way of selling them higher. I bought this "1MW", and when it arrived, it said 50MW on it, and it only cost me £15. Not bad. Here's the link for a few, they ship worldwide -

http://www.ebay.co.uk/itm/Military-GREEN-Beam-Lase...

http://www.ebay.co.uk/itm/New-Military-High-Power-...

http://www.ebay.co.uk/itm/1mW-Military-Grade-Green...

This one isn't that much more powerful than the one you showed us, but it's only £7 - http://www.ebay.co.uk/itm/Astronomy-5mW-532nm-Mili...

Hope i helped :)