Star wars? Nintendo light gun fitted with laser.

[G7PSK]

This Nintendo light gun has been fitted with a 2 watt laser.

[vk6zgo]

This worries me a lot.
Making something which say,holds a laser so you fire it,but doesn't look like something harmless,is one thing.
It is something else again to modify something which is known to be harmless,so it becomes dangerous.

[bullet308]

Hm, well, for the foreseeable future, their pewpewpew will be no match for my bangbangbang.  Unless I  cover myself in match heads...though, the eye thing becomes a real concern...

[saturation]

These are fairly easy to build and can cause quite a bit of mischief; if not retina damage, temporary blinding.  The power to burn something is less a concern than injury to the eye, its the reason such weapons were discussed and later banned by treaty.  Although the FAA tracks the source of lasers pointed at airlines in flight, its not to the point that these devices are illegal.

http://en.wikipedia.org/wiki/Lasers_and_aviation_safety

http://en.wikipedia.org/wiki/Protocol_on_Blinding_Laser_Weapons

IMHO, how-to to make weapons, from lasers that can obviously blind people, to any others, should not be advertised on youtube, a competent EE can figure out how to make a powered laser, just as anyone with basic chemistry knowledge can make explosives.  But by making it more easily accessible or suggest its plausible to others will very likely put it in the hands of users who may be more irresponsible or have a nefarious motive.