FŽanor ("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. (I'd say iceberg, but... uh, it doesn't seem suitable.)
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.
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 bordom during the grunt work that guild novices have to do.