I was thinking that a new light type could be cold, if you read the article that I have linked you see that it isn't even science fiction and because there is theoretically no limit to the amount of energy you can put into a laser and the fact that destiny is a Sci Fi Fantasy game set a couple centuries in the future I think bungie could easily add this in into the game.
In case you don't want to click the link for whatever reason here is a brief description that I have copy/pasted.
Laser cooling works because photons emitted at just the right frequency are absorbed by individual atoms heading in the opposite direction of the laser, slowing down their motion. Since atoms are very picky about which wavelengths of light they will absorb, scientists can selectively choose the type of atoms they target (and the direction in which they are moving). By reducing their motion, they lower the heat in the system, since temperature is determined by the speed of atoms in a substance (also expressed as its kinetic energy).
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It's a good idea. But what's the point really? Light type damage only really matters for burns and shield counters. Maybe cold light subclasses could have some freezing or slowing effects on their abilities but other wise I don't really see it adding much.