Sohrab is this in The Shahnameh. He smacks down a captured Persian when he (rightfully) suspects the soldier is giving him false information, then he rides alone to the Persian army, demands a single combat, and vows to hang their king!
Fëanor ("Spirit of Fire") in The Silmarillion, whose body cremated itself when he died.
In fact, the tale of the Silmarils is caused by his hot blood and burning soul. The spontaneous combustion is just the tip of the magma vein.
A villainous example: Couladin from The Wheel of Time, in the The Shadow Rising you only see him calm in only a few paragraphs and those are always followed by him raging against something. This is all the more notable because the Aiel in general are extremely in control of their emotions. Mat idly wonders at one moment how Couladin managed to live for as long as he did among them, let alone become a prospective Clan Chief.
And Perrin becomes this trope when Faile gets kidnapped by Aiel later in the series.
Don Quixote was pretty Hot-Blooded; he even gave speeches extolling giving it your all and never giving up, and doing this through force of arms.
Miles from the Vorkosigan Saga can be like this, especially as his alter ego Admiral Naismith.
In Brothers of the Snake, both Autolochus and Xander. The latter has next to no patience and is quick to get annoyed, while the former, once he's awoken, seems uncapable of standing in one place for longer than a few seconds.
Warrior Cats. Foxleap always tries to rise to every challenge, which one time resulted in the main characters having to pull him away from a fight because they were on a journey and needed to conserve energy. Eventually, he jumps to the aid of some cats fighting an eagle when told to stay back, causing one of the cats to have to rescue him and dying in the process.
Loads of examples in the Chalet School series, particularly the American girls, Simone Lecoutier and Betty Wynne-Davies. Joey is the most prominent example, and her temper gets her into trouble more than a few times, though she (for the most part) calms down as she gets older. Her daughter Margot also has some anger management issues - she refers to her temper as 'my demon', and it gets her into major trouble in Theodora at the Chalet School, culminating in Len slapping her and her dad refusing to speak to her for two weeks. After that, she learns her lesson and tries her damnedest to control it.
A Mage's Power: The greater the danger of missions, the more excited Tiza becomes. When she spots a monster twice her size, she draws her sword and runs toward it. This leads to immense boredom during the grunt work that guild novices have to do.
Wakatake of Tantei Team KZ Jiken Note. He basically lives and thrives on impulses and his performance essentially depends on his mood. Thus, while he is usually capable, he can be very reckless (such as attempting to face the convenience store robber alone in The Missing Bicycle Knows), and at times when he is down he is basically Book Dumb—which is why he's the only person in the cast who can't get into a private middle school. Remember, he's in an Academic Athlete group where being the top 2% is required.
Merik has a non-stop Hair-Trigger Temper, which causes him to act very energetically and put much more impact on everything he does.
Safi is very impulsive and doesn't hold back once she's angry.
The Stormlight Archive: Adolin Kholin is aggressive and passionate in everything he does, constantly suggesting his father fight more battles and let him fight more duels for the honor of their house, particularly in the first book. While the rest of the Alethi, having devolved into Blood Knights, see this as a good thing, Dalinar is significantly more cautious and calculating, particularly since his brother's death. Even later on when Adolin comes to understand and respect his father's point of view, he still has a hard time controlling himself.
It's shown in Oathbringer that Dalinar was arguably worse about this than his son when he was younger before a series of events caused him to change his ways. Even Adolin's brother Renarin has rushed in without considering his actions on more than one occasion despite generally being extremely calm and quiet (particularly by Alethi standards), so apparently it runs in the family.
The Raven Tower: Mawat and his father are both well-known for having high tempers, exacerbated by the fact that no one has the authority to tell them to pipe down. Deconstructed when Mawat repeatedly causes trouble for himself by acting thoughtlessly and when his inheritence is jeopardized by people who think he's not reliable enough for the job yet.
The Traveler's Gate: Alin is impetuous, entirely convinced of his own righteousness, and very powerful. It takes him most of the series before he learns even basic patience.