Okay, so basically here's what I'm coming up with so far.
Gauss Rifle replacement: Hybrid Metamaterial Rail Cannon, bit of a Fun With Acronyms - will probably find better name later
> Basically take a page from Mass Effect and store the weapon's ammo as a semi-liquid metamaterial that hardens into a magnetic metalloid solid instantly when exposed to some form of radiation or electric current. Weapon will use magnetic fields to draw and shape the projectile, allowing the weapon to effectively adjust its caliber, projectile shape, ammunition capacity, and fire rate - on the fly.
> The weapon will use a combination of standard Gauss Rifle and Coilgun designs to achieve both rapid-fire and overcharge capacities. Possible shot types are standard round of varied caliber, cluster shot, AP rod (aka crossbow bolt), cluster flechette (needle shotgun). Spent metamaterial could theoretically be recovered and returned to semi-liquid state without much trouble.
> The cost and complexity probably push it a bit higher than "basic weapon", but the increased flexibility (sadly, probably not power) should make it a worthwhile venue - besides the metamaterial, the design is fairly simple.
Laser Rifle replacement: Portable Free-Electron Laser Rifle - "Hellgun"
> The current laser rifles seem to be solid state lasers of some kind. Changing the design to a FEL introduces several possibilities.
> The operating principle of the FEL means it can create anything from X-rays, to visible light, to microwaves, with pretty much a simple turn of a knob. Variable intensity and focusing options can mean that it can be used for a whole lot of things, including nonlethal deterrent (low-intensity microwaves over wide angle).
> The power of a FEL increases with length - or, when the output is reflected back into the stream, with time spent charging up the laser. So even a compact rifle can produce a very high-power beam if given enough charge-up time. Used in conjunction with preparing a dynamic bonus to aim, the extra power afforded can be quite useful indeed.
> The design makes generator-power the most viable, since the laser is not instantaneous, and repeatedly charging up could quickly deplete any battery. However, a different design with a conventional laser (say, a hand laser emitter) to seed the electron stream can immediately produce a laser of sufficient intensity to fire, which may allow a battery-pack design to be used as well. A seeding laser can still be used with generator power too, but in both cases the quick shot can only be made on the frequency of the seeding laser, meaning that fancier things like microwaves and X-rays will still need charging up before firing.
> In short, a different design of laser optimized for generator power, with a wide range of uses and charged shot capability.
Grenade launchers and mini-rocket-launchers could easily fit R_C's third weapon type, being high-power but with costly ammunition.