This first part is sort of a wind up, skip to The Good Part for the good part.
As other posters have said before light isn't a very good weapon. But they haven't explained why that is. The reason it's not a very good weapon is because it's too diffuse.
Think of it this way, if you put a hose power (~750 watts) of power through a light bulb even if you opponent is say ~10 cm away from the bulb the energy flux hitting their body, even at its closest point is about a watt/cm^2 which would be pretty uncomfortable (it's about 4 times the intensity of sunlight), they would only end up absorbing only about 1/2 a horsepower over their entire body which is about 1/4 the intensity of sunlight.
Contrast this with spending one horsepower over one second to accelerate a human arm (~10kg) to ~28 miles per hour. Professional boxers punch at ~25 miles per hour and though they likely have the rest of their bodyweight behind that, they're not throwing one of those every second like we are here. Clearly kinetic attacks make more sense. Even if you could direct all that light into a 45 degree cone which would increase the power by about 8 times you're still not accomplishing much, especially when you realize, in order for your animal to generate that light, they have to be much closer to the light source than their opponent will be.
The only way to really turn light into a weapon with substantial advantages over kinetic bombardment is with coherent (laser) light. Coherent light stays pretty well collimated over reasonable terrestrial distances so long as it doesn't turn the air into plasma. Until very recently* there have been no biological lasers. There's probably some sort of evolutionary biology reason why this is, mostly because it's useless unless you can generate a whole lot of light (which nothing has evolved to do anyway) and have a big enough brain to aim it at a target.
*http://www.bbc.co.uk/news/science-environment-13725719
This doesn't address dazzler (bright lights which are supposed to make things blind) type weapons, in fact, now that I mention it, I'm surprised there haven't been any animals to use this. That probably has to do with the theoretical maximum efficiency of bioluminescence or something... I don't know.
The Good Part:
Anyway, none of this really answers your question, it's more of an argument for why light weapons never evolved in the first place, but let's forget the evolution part. Lets think about the traits of an animal which would use laser weapons. It would probably live somewhere with a lot open space, and good line of sight, improving this it could be a flying animal. 477
Typically most high powered lasers we have today are chemical lasers so the animal might be a big gas bag or something. I would imagine only carnivores would have a high enough calorie intake to generate laser pulses.
Hmmm... a big flying carnivorous gas bag. Where have I seen that before... Ahh yes. Allow me to present the Gas Dynamic Laser Dragon.
A Gas Dynamic Laser* (or GDL for short) is a laser which is powered (or pumped as they say in the business) by the rapid expansion of gas rather than electric discharge like most other gas burning lasers. A GDL can be pumped by the combustion of of some gas who's products are the lasing medium which is then excited to produce light which is bounced around inside a tuned cavity. The cavity is just a space with a 100% reflective mirror on one side and a less than 100% reflective window on the other. The beam comes out the window.
*http://en.wikipedia.org/wiki/Gas_dynamic_laser
Our Gas Dynamic Laser Dragon (GDLD) would, like most dragons be capable of combusting gases within itself, but this gas would be channeled downward through supersonic expansion nozzles made of bone (or preferably titanium) into a cavity which the dragon would have some muscular control over the shape of. On one end it would have a mirror and the other a window. The materials these are made of depend on the frequency of light laser produces which depends on the gas used. After the gas moves through the cavity it would leave the dragon as exhaust. If we put this nozzle/cavity/exaust system into the dragons head/neck it would be easy to aim and the beam could leave from the dragons mouth. Its esophagus could be used as the cavity if the mirrors slide into place when they're needed.
I don't know enough about GDLs to choose a good gas, but the explosively pumped GDL laser gases listed on the wikipedia page list two bio chemicals which, though at least one of them is toxic to humans, likely could be created in the dragons gut by some enzyme. 160