DS9, considered by many to be the most militaristic of the Trek series, shows strong infantry weapons fairly consistently, but is inconsistent in its treatment of ship-grade weaponry. On one hand, ship-grade weaponry seems to be little heavier than hand weapons; on the other, ship-grade weaponry - particularly torpedos - are also stated to be powerful enough to destroy planets and moons. There are a few moderate references relating to ultritium, but even these are difficult to adjust into a consistent scheme of yields.
Infantry weapons may have outputs into the gigawatt range regularly, with heavy weapons firing multi-gigajoule shots. Autotargeting features are present on Federation phaser rifles, although not on Cardassian equipment.
Ranges demonstrated are likewise mixed; although the maximum range of ship-grade weaponry clearly exceeds 100,000 km, it is common for weapons to be fired at several kilometers or even several hundred meters.
A variety of new weapons are seen. Of particular interest is the introduction of cloaked minefields and the use of orbital weapons platforms.
The Defiant's phasers appear to be generally powered by large man-portable batteries, but can also be run off of ship's power to the tune of "15% of plasma to phaser banks" ("For the Uniform"); draining the phaser banks can provide a 50% boost in speed. These two reference suggest an overall output equal to 15-50% of the Defiant's warp core output (i.e, hundreds of petawatts to exawatts.)
There are racks of these available at DS9, and it becomes quite common for a drained power pack to be replaced after a mission. These two pictures are from "Behind the Lines."
The cell appears roughly three feet long and 4-5 inches wide, making it roughly 100-1000 times the size of hand phaser power pack.
If we assume the technology used is similar to that of hand phaser power packs, then - depending on whether the batteries are recharged and drained with each shot (eventually wearing out) or nonrechargable - the figures from "Return to Grace" suggest 470 MJ to 16.4 TJ per shot. On a similar note, a satellite building up to 600 and then 900 megawatts of power and then firing downed a Runabout's shields in one hit in "Battle Lines." The total amount of energy involved would appear to be on the general order of gigajoules and no higher - i.e., not much higher than some hand weapons' power, as seen in "Business as Usual." See also the note on hand weapon power.
Plasma torpedos appear in DS9 several times; in every case, they appear exceptionally powerful. Plasma torpedos are capable of outright destroying a moon or planet in "The Die is Cast" and "Tears of the Prophets."
Romulan plasma torpedos contain trilithium, per "Image in the Sand;" this helps explain this degree of power.
In "Broken Link," we are told that the Defiant alone - which we are generally led to assume carries quantum and photon torpedos could turn the Founders' homeworld "into a cinder." Curiously enough, Worf refers to photon torpedos having "plasma warheads" in "For the Uniform," although "Sons of Mogh" indicates they still emit gamma ray bursts, as we would expect from antimatter warheads.
Quantum torpedos can be turned into long-term chemical weapons by the addition of 200 kg of trilithium resin per torpedo ("For the Uniform.") The Defiant has at least 45 quantum torpedos, although this appears to be a low figure reached late in battle ("What You Leave Behind"). "Valiant" refers to quantum torpedos having a "maximum yield," which means that quantum torpedos are variable-yield.
In "Trials and Tribble-ations," we learn the tribble homeworld was "obliterated" by the Klingon Empire. It is uncertain if this refers to physical obliteration of the planet as planned for the Founders in "The Die is Cast," or merely wiping out everything living on the surface; we learn in another episode that a Bird of Prey is unable to effectively target a subterranean base (although a Vor'Cha cruiser is able to), which would suggest that a physical deconstruction of the planet is probably not what happened to the tribble homeworld.
"What You Leave Behind" gives us another attack on planetside, although not of the incredibly destructive variety. Instead, two million Cardassian citizens are dead in seconds, with at least 800 million dead on Cardassia by the end of the episode.
Intermediate levels of firepower may be drawn from "Apocalypse Rising," in which we learn a full spread of photon torpedos would destroy Ty'Gykor and "everything within several hundred kilometers." Similarly, a 90 isoton enriched ultritium explosive would demolish an asteroid base and destroy everything within 800 kilometers in "A Time to Stand."
A gigaton explosion in empty space would apply roughly 500 kilojoules per square meter at a range of 800 kilometers - almost enough to cook frozen pizza in thermal terms, or about enough kinetically to send an inch thick (2.54 cm) steel plate flying at ~160 mph (~255 kph). At 300 km, a gigaton explosion in empty space would apply ~3.6 megajoules per square meter - enough to scorch a pizza, or send an inch-thick steel plate flying at mach 0.6. This would therefore suggest, although not require, torpedo yields on the general order of exajoules.
However, 10 isoton ultritium concussion shells can destroy an unshielded ship if they hit directly in "The Ship," but seem to have a limited effect on the surface. In order for this to be a consistent use of "isoton" as a term denoting yield, the ultritium concussion shells - if detonated underground - would release energy comparable to a 7.0-7.5 Richter earthquake. Given also that a small amount of ultritium resin in an earring has a 20 meter blast radius, the ultritium explosives of "A Time to Stand" should contain several billion times as much ultritium. If the earring contained a single cubic millimeter, then four cubic meters of ultritium should have been involved in "A Time to Stand."
In "Crossover," a hand phaser splatters Odo against the wall - a dramatic high-momentum effect, if not as dramatic in energy terms as the vaporizations of normal humanoids.
"Return to Grace" gives us a very detailed look at two typical infantry weapons. A standard Cardassian phase disruptor rifle has a 4.7 megajoule power capacity, a 3 millisecond recharge time, and two beam settings; a Federation phaser rifle is a bit larger, a bit less powerful, and has 16 beam settings, autonomous recharge, gyrostabilization, "multiple target acquisition," and other features.
Firing maximum power 4.7 megajoule shots at 20,000 rounds per minute (a 3 ms fire cycle) compares very favorably with the GAU-8 rotary 30mm cannon (used on the A-10 Warthog), which has a muzzle energy of 207 kilojoules and a peak rate of fire of 4200 rpm. The 24th century version of the AK-47 is therefore over a hundred times as powerful as a late 20th/early 21st century anti-tank weapon.
"Rocks and Shoals" would appear to show the "multiple target acquisition" of Federation phaser rifles in action. Sisko's men have "phaser locks" on the Jem'Hadar, who outnumber them in able-bodied soldiers by two to one; this is a decisive advantage, particularly combined with cover. After a brief exchange of fire, all the Jem'Hadar are dead.
"Business as Usual" gives an example quite consistent with the above. The Breen CRM-114 is a lightweight bazooka like weapon, rated to cut through 6-15 cm reactive armor and up to 4.6 gigajoule shields. This suggests shot energies in the multi-gigajoule range, which would indicate a higher power level than a phase disruptor rifle.
"Wrongs Darker than Death or Night" - an ultritium resin earring has a 20 meter blast radius. This is a small grenade by modern standards, but not very remarkable as a weapon.
"Things Past" - a chambered plasma grenade was used to attempt to assassinate Gul Dukat during the occupation. This appears to be nothing exceptional.
"Blaze of Glory" - duridium drums will hold off hand phaser fire for a while. Contrastingly, crates of gold-pressed latinum in "Who Mourns for Morn" will not hold off any weapons fire.
In "The Search" - 100,000 kilometers is "well within range" of the Jem'Hadar ships' weapons.
Cardassian system defense disruptors have a range of over 200,000 kilometers; targeting sequences may begin at 400,000-500,000 kilometers.
The Defiant's phaser beam may be adjusted to a width wide enough to envelop an entire comet. A standard burst at 10 kilometers broke the comet into three fragments, instead of evenly vaporizing it with a widebeam burst.
"Once More Unto the Breach" - cloaked, raiding BOPs close to three hundred meters before firing.
We see orbital weapons platforms most notably in "What You Leave Behind" around Cardassia Prime and also in "Tears of the Prophets." These are considered quite potent for defensive purposes, which suggests that maneuverability is of relatively limited importance in combat.