Oh, we're coming up with weapons now? Heheheheh... I have a [i]looooong[/i] list:


[hider=Weapon ideas from that sci-fi story Turboshitter is probably never going to get around to actually writing]
WEAPONS
Peacewalkers: The heavy ground weapons of the infantry, Peacewalkers are basically tankwalkers except smaller, more mobile, and slightly less well-equipped. It is perhaps easiest to think of them as giant, house-sized suits of power armor. Piloting them is easy for bipedal humanoid species (or whichever body-type the suit is built for), which makes them favored over the slightly clumsier tankwalkers, and equipping them with a wide variety of weapons is easy. They're incredibly strong and deadly, and function as a form of hypercompetent backup for the long-range tankwalker bombardier formations. In fact, it's often said a peacewalker at close range can do even more damage than a tankwalker at long range, even to tankwalkers themselves. 

Tankwalkers: The ground vehicles of the infantry, tankwalkers are slow, cumbersome, and large, but also carry the most firepower possible in a ground vehicle, making them deadly weapons on the battlefield. Often compared to mobile artillery platforms, a tankwalker can defend itself at close range but is primarily designed as a long range weapon, equipped with high-powered chemrail autocannons with smartfire technology, drones and guided antimatter warheads. 

Drones: The go-to weapon for large-scale warfare, drones are disposable miniaturized automated weapons, sporting primitive onboard simulated intelligence and a vast arsenal of weapons. They are capable of hypersonic flight and relativistic acceleration over time and can achieve speeds vastly in excess of escape velocity to pursue targets beyond the atmosphere. Boasting a list of features like mounted anti-missile and anti-personnel lasers, VEX rocket pods, machine guns, and even cheap shielding, drones can be fired like bullets from a Tankwalker's mounted turrets and like missiles from the shoulder pods of Peacewalkers, and can function as both. Even with their weapons disabled, drones are formidable weapons, capable of killing targets with pinpoint accuracy through sheer kinetic energy alone. The primary weapons of the future, drones are what separate mercenaries and militia from a true armored regiment.

Boltguns: The most common model of weapon available in the public and private sectors. Keeping with the general philosophy of "directed kinetic energy weapons are cool", boltguns are essentialy handheld chemrails which accelerate tiny (or sometimes not so tiny) tungsten projectiles to high-hypersonic velocity, often in excess of 8-11 km/s for civilian models, to subdue soft targets with minimal shielding. The name comes from the ablation process the rod undergoes when the immense heat and atmospheric friction start to literally ionize the projectile, creating a distinct tail or "bolt" of plasma that follows the invisible piece of tungsten metal. Boltguns are quick, clean, and efficient when used in atmosphere, leaving little to no evidence as to the projectile used, which has long since melted or been reduced to a sliver of metal smaller and thinner than a fingernail. They also have excellent piercing power compared to the weapons of the early second Earth millenium, with an average kinetic energy of 1-15 MJ (for the pea shooters) packed in a projectile no larger than a bead, and hollow-point bullets allow the boltgun to function like a modern-day grenade launcher, the bullet collapsing on impact and releasing its kinetic energy outwards in all directions like a hand grenade (needless to say this kills the target, and is also great for demolishing walls and other obstacles behind them).

Plasma casters: The flamethrowers of the future, plasma casters take advantage of plasma's tendency to disperse and dissipate a certain distance from its source and turns it into a deadly close quarters weapon, capable of flinging jets of ultra hot plasma for up to 30m away from the wielder. Or in other words, this is my plasmawerfer. It werfs plasma. Originally intended as an industrial tool, plasma casters are almost exclusively used as weapons now, and are hard to obtain, difficult to use, but very effective for causing destruction and terror. Allowing the magnetic containment cage to fail is not advised, unless you're fond of the adrenaline rush of cooking a VEX grenade inches from your face.

VEX: Variable EXplosive. Also called VEX grenades (a misnomer since a VEX grenade is merely a grenade with VEX in it), this revolutionary gaseous high explosive can be programmed for a specific, pre-set yield and blast shape before detonation, allowing unparalleled precision and accuracy. As the name implies, VEX is variable, and uses directed bursts of unstable plasma shaped by a powerful electromagnetic pulse to suit nearly any soldier or explosive expert's needs. However, standard factory-setting VEX comes in distinctly shaped and sized packages with a maximum blast radius of 4km. Extra-large blast radii or unusual shaped detonations must be programmed manually. VEX is not commonly available to the average citizen of the Milky Way, but can be easily obtained on the black market.

SUPERWEAPONS 
Higgs bullet: A relativistic kill vehicle that relies on an onboard Higgs field manipulator capable of triggering an explosive increase in mass. By firing the lightweight drone missile at relativistic speeds from a mounted chemrail and activating the Higgs field manipulator picosceonds before impact, speed is preserved while mass is increased and the projectile impacts with the force of many nuclear bombs. The largest Higgs bullets can smash countries and scar entire continents, suffocating worlds in clouds of superhot microdebris.

Nanohazard: The "controlled" release of nanomachines with no preset replication limit. The early stages of terraforming and most mining operations are classified as "nanohazards", although their use as weapons is far from unheard of.

Singularity bomb: The ultimate superweapon, a bomb capable of destroying entire planets in minutes. While some civilizations have the means to harness conventional energy in excess of 300000 zettawatts (enough to obliterate an entire continent in a single microsecond burst along with a planet's ecosystem) and channel it into directed energy weapons, destroying a planet this way is time-consuming, and not efficient or frightening enough as a weapon of total war. A singularity bomb is different. By creating a black hole the size of a marble at the center of a planet, one of these weapons can lay an entire world full of sentients to waste in under fifteen minutes, with no hope for escape or salvation. Once a singularity bomb is used, nothing will survive. Ships get pulled in by the gravity, their drives unable to form a stable warp bubble in the immense gravitational tide of the singularity, and everything on the surface of the planet dies as it breaks down from the inside out, collapsing in on itself and exploding before silently fading into debris passing the event horizon.
[/hider]

Feel free to take your pick.