Generally speaking Beam weapons seem to be the weakest of the weapon types in Eclipse Phase. Kinetic weapons have a lot of flexibility, and kind of serve as a reference point for how good a weapon is as a result. Spray weapons have Shredders, with their extreme close range damage for a low cost, and some really interesting utility heavy options. Seekers are the gold standard for long range damage and heavy weapons.
Beam weapons don't seem to have much of a role. There's a lot of less-lethal options, but only the laser pulser has one which works on synths. The category also includes the particle bolter and plasma rifle, which deal respectable and extreme damage, while having a high cost. The current role which beam weapons occupy is high base damages, and good use in vacuum. Every other weapon category also has good nonlethal options. Zap rounds, freezers, overload seekers/grenades, etc, so that's not really a unique role.
I have some proposed changes for beam weapons to help them carve out their role a little bit more.
The laser pulser is actually a quite respectable pistol/SMG, as it almost has the damage+AP of an automatic rifle when concentrated, giving it a ton of damage against poorly armored targets, while having an easily used and concealed one-handed form factor. The biggest problem with laser weapons is that they lack a rifle. With that said, here's a proposed stat block for a laser rifle:
Damage: 2D10+5  AP:0 ammo: 100 SS,SA. Uses the same range brackets as the rail machine gun. Cost: twice as much as a typical laser pulser. . This weapon requires two hands to use, and due to its large lens has a bulky form factor, making it hard to conceal.
The damage on this weapon is designed to be similar to the laser pulser/automatic rifle comparison, but matches the sniper rifle's damage+AP in raw damage. It's a good choice when engaging durable, but poorly armored targets, and like all laser weapons, has an extremely long range in vacuum. Makes a good spacewalk sniper.
I also want to change the rules of the particle beam bolter and plasma rifle, largely to make them a little more physics-friendly, but also to fill some current gaps with the weapon choices available.
For the particle beam bolter the change is simple replace the current AP with [target's armor/2+2]. When firing on a target wearing heavy body armor with a helmet (16/16 armor), the particle beam bolter has an AP value of 10 (16/2+2). When firing on a battlesuit [21/21] the AP value is 12. [High]
This makes the particle beam bolter a valid weapon against practically any target, making it a good option if you want to be able to deal damage, and don't know what you'll be up against. It retains it's current strong damage code, which combined with it's exceptional AP makes it a strong general purpose weapon. Seems fair for 5000 credits, as it's competing with seeker and sniper rifles at that point.
Finally, the weapon makes more sense this way, as there is no armor proof against a relativistic charged particle beam. Effective armor just produces x-ray spalling, which isn't feasible to shield against on a personal scale. This is a simple rule designed to emulate this all-penetrating quality.
Similarly, the plasma rifle just doesn't make a lot of sense. Plasma is general not very energy dense, and cools super rapidly when it expands. It's just not very dangerous stuff except in huge quantities. Fun fact, the sun only has about the energy density of a compost pile per cubic meter, it's just huge. The current role of the plasma rifle as a single target huge damage dealing is quite a bit more soft-sci-fi than most of the weapons, and shares a lot of it's physics with the particle beam bolter. A hard(er) plasma rifle would basically be the particle beam bolter. I'm not super interested in slavishly forcing pure realism, especially when cool and unique weapons can exist, and I want to respect the Eclipse Phase tech base's abilty to make *really* hot plasma so here's my take.
Plasma blaster: damage 2D10+20, cone, blast, ignite AP -8. Uses the same range brackets as the torch. The plasma blaster fires a magnetically contained plasma torus, while the containment and stability of the torus fails extremely quickly, it still superheats anything immediate to it while it fails and dissipates. Like a plasmaburst grenade, this weapon deals it's full listed damage to swarms. It also has a 1 meter radius blast. Keeps the ability to set targets ablaze. SS/SA [Expensive]
This version of the plasma rifle can actually deal more damage against clustered targets at extemely short range. Remember that cones can hit multiple targets at short range, and the blast will center on both targets hit, allowing overlap. It also serves as a unique weapon for keeping pesky swarms from eating you or your gear. Wear good thermal armor when using this weapon. It's basically a shotgun weapon with even more damage, and video game tier range brackets. Still deals 20 flat damage at 50 meters, and deals a peak of more than 100 damage to clustered targets within 5 meters of the user. I think this might be overtuned, but it's finally a weapon which can actually threaten small vehicles.
The stunner doesn't change, it's already insanely good against a limited range of targets, and it super cheap.