Right off the bat, the Light Plasma Pistol proves itself to be a very powerful weapon. While not terribly damaging shot-by-shot, it makes up for this by having a surprisingly high fully-automatic rate-of-fire. Coupled with a sizable magazine, this weapon can easily shred any enemy unfortunate enough to be caught in the crosshairs, be it a damaged Sectopod or unarmored Muton.
That being said, the Light Plasma Pistol's blazing fire rate goes both ways: it also causes the weapon to burn through ammo at an alarming rate, and might cause problems to those who are not diligent at scouring for ammo pickups. Furthermore, it still takes a handful of shots to down just a single target, so often times an entire magazine must be spent to score a kill (and some times even more than that). Lastly, because it is a promotional weapon, it does not spawn in the environment at all, so the only way to re-acquire it should the player decided to swap it out is to find a Resupply Station, which is to say not very common.
This weapon becomes available to players who pre-ordered the game from GameStop upon completion of the mission to rescue Dr. Weir. DLC owners will likewise receive the weapon under the same circumstances.