While Dune is certainly famous for swords and knives (with or without shields), there are a few handheld weapons that can do some damage from a distance.

Herbert being Herbert, there's not much in terms of technical specifications. There's plenty of scenes across his books where a character would be described holding "a gun" or a "a pistol" without so much as a caliber, let alone a manufacturer.

But we do get some that are described in a little bit of detail.

Heads up: today's edition will be one for the purists, meaning we're only focusing on the core canon and skipping the chandler pistols and cellguns of the expanded universe and the weirding modules (do we consider those guns?) of the 1984 movie.

Lasguns

Lasguns are the do-it-all energy weapons of Dune, firing white hot laser beams to cut through anything and everything. Except of course, shields.

LASGUN: continuous-wave laser projector. Its use as a weapon is limited in a field-generator-shield culture because of the explosive pyrotechnics (technically, subatomic fusion) created when its beam intersects a shield.
— Terminology of the Imperium, Dune [1965]

Fire a lasgun at someone wearing a personal shield, and you get subatomic fusion at both the shield and the lasgun itself. The result? Two explosions, unpredictable yield, and a very dead everyone within blast radius.

Sometimes it's a firecracker. Sometimes it's a nuclear bomb. The uncertainty is the main deterrent.

We know that (just like shields) they have adjustable intensity settings, from narrow cutting beams to broader, more destructive blasts.

Setting his lasgun on maxibeam, Teg pressed the trigger. A fiery arc swept across the slope below him. Trees burst into flame and crashed. People screamed. The weapon would not perform long at this discharge level but while it did the carnage produced its desired effect.
— Heretics of Dune [1984]

And while they're the only energy weapons on this list, there's a surprising amount of variation to them.

In Heretics alone we get long lasguns, large lasguns, small lasguns, bulky lasguns, armored lasguns and a lot of field-style lasguns - whatever that might mean, since we don't get really get a description of their differences.

The battle beyond the buildings grew louder. He heard hoarse shouts, the high hissing of burners and the lower buzz of large lasguns mingled with tinny zip-zips of hand weapons.
— Chapterhouse: Dune [1985]

Maula pistols

We know from Languages of Dune research that maula means "slave" in Fremen. Having said that, there's no canonical explanation for why the spring-loaded gun of the Fremen would be called a maula pistols.

My headcanon is that it's what slaves would've been able to cobble together from scraps but I'd be happy to hear your interpretation.

MAULA PISTOL: spring-loaded gun for firing poison darts; range about forty meters.
— Terminology of the Imperium, Dune [1965]

We know for a fact that these guns don't make a zip-zip sound.

Ghanima thought of using the maula pistol, but its characteristic sound would be sure to attract unwanted attention.
— Children of Dune [1976]

The characteristic sound, and given the spring-loaded action it makes perfect sense, is a loud spat.

[Jessica] rolled away from the crashing throne as she fell, came to her feet as she heard the sharp spat of a maula pistol . . . and again.
— Children of Dune [1976]

Stunners

STUNNER: slow-pellet projectile weapon throwing a poison- or drug-tipped dart. Effectiveness limited by variations in shield settings and relative motion between target and projectile.
— Terminology of the Imperium, Dune [1965]

Which basically means that in certain conditions, stunners would be able to penetrate a shield.

Unlike the maula pistol's spring mechanism, stunners appear to use more sophisticated propulsion - maybe a gas-actuated system that can adjust the projectiles' velocity?

Whatever the case, stunners were the standard military sidearm, carried by House soldiers and Sardaukar alike.

When Liet-Kynes first observes the Atreides guard on Arrakis, he notes they're "heavily armed - slow-pellet stunners, swords and shields." During the Harkonnen attack on Arrakeen, Thufir Hawat observes Sardaukar troops carrying "a knife in one hand, a stunner in the other."

The weapon's name suggests non-lethal intent, but those "poison- or drug-tipped" darts can be loaded with anything from sedatives to lethal toxins. The stunner's role seems to be providing ranged support for the blade-work that defines usual shield combat.

Dartguns

Not something we see a lot - but something that has canonical significance.

A numbing shock slammed [Leto's] arm aside. He felt pain there, saw a dart protruding from the sleeve, sensed paralysis spreading from it up his arm. It took an agonizing effort to lift his head and look down the passage.
[…]
Yueh began walking toward him, pocketing a dartgun.
— Dune [1965]

Unlike the maula pistol's spring mechanism or the stunner's more complex propulsion, the dartgun's specific mechanism isn't detailed.

It seems though that it must be something silent, and as such, perfect for ducal take-downs and other types of assassinations.

Cutteray

CUTTERAY: short-range version of lasgun used mostly as a cutting tool and surgeon's scalpel.
— Terminology of the Imperium, Dune [1965]

Officially not a weapon and depending on its size it can be used both in mining and in surgery. But since it's basically a lasgun, I'm sure the same rules apply.

Baradye pistol

We'll finish with my absolute favorite pistol in the whole of Dune: the baradye pistol. Which is a pistol in name only.

BARADYE PISTOL: a static-charge dust gun developed on Arrakis for laying down a large dye marker area on sand.
— Terminology of the Imperium, Dune [1965]

Although I'm sure that you could cause considerable harm, if you'd unload it on someone at short range.

We see it exactly once in the books, when Paul checks the contents of his Fremkit when they're fleeing to the deep desert with Jessica.