You can't think of any reasons that are constructive instead of destructive? And you BUILT that thing?
Here, let me fix that. Starting with this model ...
* Stage magic FX. Works great with the flash paper and chemical items.
* Science class demo. If this doesn't make 'em love optics, nothing will.
* Carnival games. Because it's cool, that's why.
* Performance art. Basically what this video already is, but I'm sure an expert could add even more wow.
* Signalling. Lasers are already used for this purpose. Stronger ones go farther.
* Sculpting things. This one might be interesting for ice sculpture.
* Spiritual applications. I could so write a ritual around this thing. Yes, I've done science rituals before.
* Cooking. Let's make s'mores. Heck, I know geeks who could probably write a program to cook your marshmallow to your exact specifications every time, like a good toaster. Hmm, not sure it would taste right though; marshmallows really benefit from that smoky note of a campfire. Okay, you could boil water with this gun. Cook anything that benefits from flash-searing. I'm sure a decent chef could make use of it, they cook with blowtorches now.
Now imagine a more powerful laser gun ...
* Quickly clear debris from streets after a storm. Hey, let's mount them on emergency vehicles! Also my SF colony Common Ground has had laser snowplows since I was in college.
* Cut trapped victims out of a wrecked car. Bonus if you hook up a scanner and computer to calculate where and how to cut without hurting anyone, because right now the Jaws of Life are a little risky.
* Industrial uses such as cutting or welding metal. More precision = yay.
* Laser-powered spaceships. I'm still fondly remembering presentations by Travis Taylor.
* Now we can sculpt stone or metal. Neato.
Seriously, how can people not think of good ways to use technology?