Direct energy weaponds.
Weapon Descriptions

Laser (Light Amplified by Stimulated Emission of Radiation)
Lasers are the mainstay of most sci-fi/high tech games out there. They are simple, elegant, and cheap weapons compared to most other energy weapons in sci-fi. Simple because there is no need for massive cooling, heating, compression or other such equipment, just a focusing chamber of some sort.
Elegant due to the precise damage that it can inflict and the lack of sound by conventional physics other then a slight hum. And cheap for the same reasons it is simple, the lack of complex systems.
Lasers inflict damage entirely through exciting the molecules in the target to a higher state of action. In other words, it burns either a nice hole or melts a section away due to high heat in targets with low water concentrations and causes targets with a high water concentration to undergo explosive vaporization of the targets fluids. So upon hitting a high density composite armour, the laser causes an area on the armour to melts away, revealing either a deeper layer of the armour or exposes whatever is underneath the armour to further damage, whether that is structure of the item or the poor pilot.
hile being a very effective weapon under optimal conditions, the laser drops in effectiveness under adverse conditions. Optimal conditions for a laser are conditions not found within an atmosphere. Environmental factors including particles in the air, humidity, and other common occurrences, when combined, render the laser as a weapon best suited for use in outer space. Particulate matter in the air tends to scatter the beam, reducing the amount of energy that arrives at the target location; this lowers the amount of damage done to the target (no duh). Humidity in the air poses another problem for the use of lasers in an atmosphere. At the front shock-cone (the point where the laser is moving through the air), the temperature is high enough that it can no longer hold humidity and the rapid cooling of the air after the beam has passed through, result in an interesting phenomenon. This causes the humidity in the wake of the laser to condense into a fine line of mist in the shape of the beam in the air for approximately 2-6 seconds afterwards. This is known as a DEW (Directed Energy Weapon) Line, and provides everyone in the area with a straight line between the target and the firing unit.

Ion Weapons

The category of Ion weapons covers a broad spectrum of weapons. These types of weapons are slightly higher up the technological ladder compared to lasers, but not by much. They use most of the same systems as a laser with the addition of a system to gather and compress ions from either the surrounding environment or from a special reaction mass container. The addition of the compression system increases the weight, bulk, and cost and reduces the range of the weapon when compared to a laser. But these reductions are offset by the significantly higher damage potential and reduced energy requirements of the weapon. Firing a stream of low mass, low energy ions, down an ionized path to the target, ion weapons are related to the more advanced particle beam type weapons.
While a laser does damage through extreme heat, Ion Weapons acts almost as a sand blaster at the point of impact. The particles in the ion stream wash across the target surface, stripping particles from the target. A secondary effect of Ion based weaponry is an electrifying effect caused by the interaction of the ion beam with the target surface. While not damaging in itself, this effect can be quite horrifying to watch as ultra-low power lightning bolt crawl across the surface of the target.
Overall, an ion weapon is as effective as a laser weapon. While a laser weapon suffers due to particulate mass between the weapon and the target, the ion weapon actually functions better with the intervening particle mass. This is due to the particle mass in the way being added to the beam, replacing ions lost at the trailing edge of the beam. While humidity poses a much lower problem to an ion weapon, the problem of DEW Lines is still inherent, though not quite as obvious or as long lasting in the air. While the laser is a weapon best suited to use in a non-atmospheric environment, the ion weapon is best suited for use in terrestrial conflicts. To simplify the production of most ion weapons and to also lower the weight of the weapon, most ions would use some method of collecting the ionic mass for firing from the air around it. While effective in an atmosphere, in space, this tends to have no effect.

Plasma Weapons

Contrary to popular belief, Plasma is not super napalm. Nor is it some sort of ultrahigh temperature gel generated within the gun. Plasma is another way of looking at matter beyond solid, liquid, and gas. By the simplest definition, plasma is ultrahigh temperature substance somewhat like a gas and a liquid at the same time.
Plasma cause damage not only through high-energy discharge on the target, but also through extreme heat, severe ionic charging of the target surface, radical decomposition of any organic or semi-organic components of the target, among other forces. The high-energy discharge makes reference to speed and mass striking the target, resulting in damage with no equivalent in modern weapons. A 50g (1.5oz, about 1/9th of a pound) cadmium telluride pellet turned into plasma would have more damage upon impact then a 150mm tank shell. The standard plasma weapon used in Rifts is what is sometimes known in physics as a "Free-range Plasma" (FrP) weapon. This type of weapon uses ambient molecules and energy from some source to form a high-energy plasma, which subsequently ejected from the weapon at high-speed at the target.
While achieving incredible amounts of damage, Plasma weapons are among the least power effective weapons in existence. This is primarily due to the weapon having to gather enough mass together, and then heating the mass up to the point where it becomes plasma. Another drawback of this type of weapons is DEW Lines, a problem for all types of energy weapons. Whereas the DEW Line from a laser or ion weapon is a short lived phenomenon; the DEW Line from a plasma weapon has additional problems. The DEW Line from a Plasma weapon has a medium to long duration within the air, along with residual ionization effects of the air through with the Plasma weapon was fired. The residual ionization of the air can be detected long after the weapon was fired. This same ionization can lead to an increased number of lightning strike in the area that weapon was discharged for up to an hour after firing. An additional drawback inherent in plasma weapons is recoil. Unlike most of other types of energy weapons, plasma weapons expel enough mass each firing to achieve recoil. While the level of recoil is lower then that of a conventional rifle, persons used to laser and ion based weapons tend to be surprised by the weapon kicking when fired.

Particle Beam Weapons

An outgrowth of both Ion and Plasma weapons, Particle beam weapons are among the pinnacle of energy based weapons. Firing a beam of heavier particles (Iron, Iridium, Cobalt, and Tungsten nuclei) at the target, Particle Beam weapons cause severe damage by numerous principles. The primary cause of damage is the impact of the particles in the beam. This causes effects close to that of an Ion weapon, the removal of layers of the target's surface. In the case of Particle Beam weapons, the damage is much higher then that caused by Ion weapons. This is due to the larger and heavier particles that compose the beam. The secondary cause of damage by a Particle Beam is severe ionization of the target. This is a much more damaging effect then the similar effect produced by Ion weapons. The ionization produced by a Particle Beam weapon is comparable to that produced by a direct strike from a lightning bolt. This can cause electronics to fail, organic material to decompose into their components, and other effects.
While being a devastating weapon, Particle Beams do have significant drawbacks. While a laser, ion, or even, to a certain extent, plasma weapons, all do generally the same amount of damage at all ranges, Particle Beam weapons experience a drop in power with the distance traveled. At extreme range, a Particle beam will only produce the ionizing effects, this is due to the particles in the beam having either lost most of their energy or having been lost from the beam. This can be countered by the lengthening and finer focusing of the Particle beam, but only to a certain extent. Another drawback is the high power requirements of the beam itself. While a laser or ion weapon requires very little power, a Particle beam requires significant power.