The Skrill from Dreamworks Dragons.
The Skrill is an elusive, Strike Class dragon. According to the Book of Dragons, it is one of the most mysterious and formidable dragons. It is also one of the most powerful of dragons, being among the smartest, rarest and fastest dragons. The Skrill is aggressive, powerful, and nearly untrainable. It seems to be almost as feared as the Night Fury, if not more feared. This reclusive dragon is belligerent and as unpredictable as lightning strikes. It is very territorial, despite following stormy weather; Skrills do not breathe fire, instead they channel lightning down their metallic spines, firing it from their mouths in a show of destructive blasts. If you find yourself flying through a thunderstorm, watch out! Despite it's smaller size, Skrills can give as good as they take, and they can take a lot.
Smaug the Dragon from J.R.R Tolkien's novel The Hobbit. He was a fearsome Dragon who invaded the Dwarf kingdom of Erebor 150 years prior to the events described in the novel. A group of 13 Dwarves mounted a quest to take the kingdom back, aided by the wizard Gandalf and the Hobbit Bilbo Baggins. Smaug is described as "a most specially greedy, strong and wicked worm".