The laser rifle, sometimes called the laser or sniper rifle is a long-ranged weapon that can only be used by the scout armor to kill targets from far away. The laser rifle is an energy-based weapon that fires a straight red laser at (effectively) the speed of light. It uses no ammo, but the red laser remains visible for a second, allowing enemies to spot where you are. The damage dealt by the laser is directly proportional to how much energy you have at that moment, and when fired, instantly drops your energy to zero. It's the most effective long-range weapon in the game, and can still be used effectively at any range. In duels, it can be complicated to use because of the fact that it drains all of your energy, but players with high accuracy can overcome this hurdle.
Usage
Disc Sniping
Disc sniping, while often looked down upon by most of its victims, is a popular method of killing/injuring an unsuspecting player by combining the spinfusor and the laser rifle. A player would fire a spinfusor at his target, then, right before the disc would hit, he would snipe his target. This method often kills other unsuspecting snipers in one hit, and injures heavies/mediums. This tactic is rarely used in competitive play because most people don't stand still for the length of time it takes the disc to reach it's target. However, in pubs, you may find it to be a slightly entertaining moment.
Flag Retrieval
The laser rifle is a very good tool to injure or kill the enemy flag carrier. Often, when taking the flag, the flag carrier (usually in scout armor) is injured enough to be killed by a good torso or head shot from the laser rifle. When the flag carrier skis, (s)he is often more concerned about gaining speed to outrun his/her chasers, rather than zigging and zagging to avoid fire. Most snipers take advantage of this by standing behind the flag carrier facing the direction they are heading. This makes sniping easier, for the sniper only has to aim up and down instead of left, right, up, and down.