As he pointed out, kinetic energy is the most efficient (known) method of imparting destruction to a target. For the most part, if you want to use something besides a gun, you're going to have to make your weapon bigger than an equivalent-damage gun.
That doesn't mean that some things are not more vulnerable to some forms of energy than others, of course. Indeed, the usefulness of light-swift beams makes them highly desireable for trying to hit targets that are beyond visual range (regarding space combat, at least). The relative inefficiency is more than made up for by the greater capability.
This is like saying that infantry is the most efficient use of your military dollar, but you can do plenty of things with aircraft that infantry can't do (yet). Their added capabilities more than make up for their lower efficiency.
So how many ways are there to impart lethal energy to a target? Plenty.
Light (lasers)
X-rays (xasers)
Microwaves (masers)
Disintegration by charge suppression
Disintegration by strong-force negation (a lot harder)
Particle streams (hydrogen atmos, anti-hydrogen atoms, mesons, neutrinos/antineutrinos, etc)
Nuclear radiation (usually delivered by nuke, but can also be in the form of a powder or just thrown in chunks, kind of like DU shells that weren't depleted)
Gravity waves (crush your target)
Jump Projector
Plasma projector
Fusion projector (standard FGMP or throw a hydrogen pellet at some one and then lase it)
Lightning (tricky)
Heat (flamethrower, "heat ray", flare gun)
Cold (liquid helium spray, probably not useful against armor)
Poison (chemical)
Bioagent
Nano-Dissassembler (nasty stuff!)
Acid (natural or unnatural)
EMPs (usually delivered by nuke)
Flashy lights tuned to the nervous system of the target species (imparts epileptic convulsions)
And the ever-popular: throwing a gas-giant at your home star (not as hard as a lot of fantasy equipment, like singularity guns and exotic-energy weapons.
I'm sure there are plenty more. Most of these things are going to give no benefit, or be impossible or impractical, like differentiating between NOTAR technologies for helicopters. Only one is really needed, the others are mostly different ways to acheive the same thing. So pick a couple things you like and stick with them; no need to have 100 different ways to do one thing when 5 is plenty.