Firebenders, obviously. A select few also have secondary abilities like lightningbending and combustionbending. The interesting part is that not all of them fit the hot-tempered mold that usually goes along with fire powers, given that they are an entire culture. Zuko is plenty hot-headed, but his sister Azula is more cold and cunning, which her blue fire reflects. Their father Ozai is somewhere in between, while Iroh has the personality of a warm campfire.
Aang, on the other hand, once he accepts that Firebending does not equal Bad Powers, Bad People, comes fairly close to Iroh's version of this, though he does become considerably more focused; it's implied that Firebenders have a tendency to become overly intense and Determinators.
The Fire Nation's philosophy of firebending via rage plays a part in their hot-headed tempers; the Sun Warriors, the original Firebending civilization, passed onto Iroh, Zuko, and Aang the original, life-affirming form of firebending that averts the need for firebenders to be Hot-Blooded to use their powers. It is indicated that this style of firebending allows for far more control than rage-powered firebending does.
Then there's Mako from The Legend of Korra, who's The Stoic ("cool under fire," as a sports announcer puts it). Avatar Korra herself fits the Hot-Blooded stereotype, and it's interesting to note that she will default to fire even though she's a Waterbender by birth.
Korra reveals that the Avatar cycle actually began with a firebender. Avatar Wan was born in what would eventually become the Fire Nation and it is the first element he learned after being given the power by the lion turtles. He even has the Supernatural Gold Eyes most of the other Fire Nation characters have.
Inferno from Beast Wars, right down to being a fire ant.
Heatblast from the original series is an alien made of flames that can breathe, absorb, and manipulate fire in general.
Swampfire from Ben 10: Alien Force can shoot fire from his hands. His ultimate version from Ben 10: Ultimate Alien can also throw the combustible sap from his body and light it on fire on top of his enhanced fire power.
Dragamonz: The Firewings have moves based around fire, ranging from fireballs to summoning a volcano from the ground.
The Fairly OddParents! had Super Bike, who could transform into a dragon form that breathed fire. Naturally, this form came out when he was angry.
The Hollow: Kai after their time in the theme park, he develops the power of manipulating and generate fire.
Jackie Chan Adventures: The Dragon Talisman possesses the power of combustion. Whoever wields it can shoots fire from their hands.
Lucius on Jimmy Two-Shoes sometimes shows the ability to do this, but it's mostly treated as a Running Gag when he's angry. Word of God says he has some powers he refuses to use out of pride. Presumably, this is one of them.
In Mighty Ducks: The Animated Series, Wraith is the last of the Saurian warlocks. His primary attack spell is a thrown fireball that explodes with the force of a grenade on contact with a surface, and he teleports by fading into or out of a cloud of smoke. When not in battle he tends towards the Fiery Stoic personality. Another sorcerer, Asteroth, can turn into a dragon and straight up breathe fire.
Monkie Kid: The hot-headed Red son lives in a fortress surrounded by lava, using his powers like flame throwers in combat and formerly possessed the Samadhi fire, a raging flame so powerful it could tear apart the very fabric of reality. He can also "Pyroport" using them.
Being a dragon, Spike has fiery breath, and has used it a few times — including melting a lock in "Inspiration Manifestation" and quickly melting a falling ice mass in "Equestria Games". But it wasn't until the fourth season that he used his fire breath to do much more than send scrolls, and he doesn't have anything like a hot-blooded personality.
The Kirin are pony-like creatures who turn into the fire-maned Nirik when they get mad. Before learning to control their emotions, they burned their village down and took dips in a magic stream to stop themselves feeling emotion at all.
The Powerpuff Girls: Blossom's special power is the ability to breathe fire and ice, although it tends to switch depending on the weather and her body temperature. (She doesn't use it much, though.)
Star Wars Rebels reveals that Force Fire exists, but is only used by Emperor Palpatine.
Wasabi from Sushi Pack has the power to shoot fireballs at his foes due to the fact that he's a spicy ball of hot mustard.
Transformers: The Dinobots are fire-breathing robot dinosaurs. Appropriately enough, in most continuities, they tend to be very ferocious and hot-blooded. Despite all of them usually possessing this ability, it's most associated with the Triceratops Slag.
Bloom from Winx Club has fire-based powers that can manifest in the form of fire dragons, fireballs, fire beams, firestorms and explosions at varying intensities. Justified because she has the mythical Dragon Flame power.
Taranee Cook from W.I.T.C.H., again. Like her comic book self, she is no hothead, instead being reserved and intelligent. Also, before she got her powers, she was afraid of fire.
