The Book of Revelation has the Two Witnesses (who are about as uncorrupted as mere mortals could be), who stand around outside the Temple and breathe fire on anyone who tries to harm them. They're two olive trees and two candlesticks. With mouths. Symbolically.
The Chimera is described in The Iliad as "a thing of immortal make, not human, lion-fronted and snake behind, a goat in the middle, and snorting out the breath of the terrible flame of bright fire" (VI. 179-182).
In The Cycle of Fire, the Mharg demons have a breath weapon that reduces all life to slime, and leaves the land barren for decades afterwards.
Madame d'Aulnoy's fairy tale The Yellow Dwarf includes two giant turkeys that can breathe fire. These turkeys pull the cart of the titular dwarf and the Fairy of the Desert.
In Robin Hobb's fantasy world, dragons breathe a mist of strong acid.
Dragons (and their ancestors, fire lizards) in the Dragonriders of Pern series can breathe fire, but as this is a Science Fiction series rather than Fantasy, it has a mundane explanation. They chew a naturally occurring rock, named "firestone", and swallow it into a specialized stomach that mixes the pulverized stone with special acids, creating a pyrophoric gas that can be expelled from the dragons' mouths. Their capacity for this gas is limited, so their riders carry sacks of firestone to resupply them in flight.
In Fablehaven, the fairy dragon, Raxtus, feels useless because his breath makes flowers grow. Compared to his father Celebrant, who has at least five separate breath weapons. We see a few dragons breathe fire, but there are also ones that breathe poison or Truth Serum.
Dragons in Septimus Heap breathe flammable gases, and their first breath is also flammable.
To the Kantri of Tales of Kolmar, fire breaths are something sacred, used to consecrate things, though this doesn't stop them from using it to light comforting fires and expelling it in bursts of emotion, analogous to human laughter and tears.
In Trapped on Draconica and Legacy of the Dragokin there are a race of humans called Dragonkin, who were granted powers of the dragons. They have different breath attacks (fire, ice, wind, etc) depending on the dragon they were based on.
Most dragon breeds in the Temeraire series don't have any kind of Breath Weapon, and the ones that do are particularly prized. The stars of the British Aerial Corps are its Longwings, who can spit acid.
When fully grown, Temeraire himself can roar hard enough to knock things down, which marks him as belonging to an even rarer Chinese breed than anyone previously thought.