Both Game of Thrones and House of the Dragon have introduced exceptional fighters. Though characters have used unique weapons, like Arya Stark's Valyrian steel dagger, swords are still the most common weapon in the Game of Thrones universe. They come in all shapes and sizes, with varying levels of history and legacy tied to them.
Beric Dondarrion is often overlooked as an important Game of Thrones character, but he's undeniably interesting. His conversion to worshiping the Lord of Light gives Thoros of Myr the means to resurrect Beric every time he is killed. When Beric engages in combat, he wields a flaming sword, supposedly using magic granted to him by the Lord of Light.
It is an epic spectacle and helps him keep up with those holding Valyrian steel weapons or Dragonglass against the White Walkers. Beric's flaming sword is assumed to be an alternative to the legendary Lightbringer sword from the books. It's the best and most visually impressive sword in Game of Thrones.