Lightwing

There is conflicting evidence as to whether the Lightwing is a species of dragon or a proper name for an individual dragon, mentioned once in "How to Fight a Dragon's Fury".

When the Viking forces charge in to fight the Dragon Rebellion, there is -

"Barbara the Barbarian on her Lightwing, her cat balancing in the dragon's head."

This reads, like so many other once-mentioned dragons, as a dragon species name. Lightwing is not mentioned again.

However, an image of the Viking dragons with their riders charging into battle is also provided in Book 12: Though rather masculine in this depiction, the rider is most likely Barbara the Barbarian. The dragon however, looks like a Rocket Ripper, even by the way the Viking is riding this dragon. Another possibility is this is another member of the Barbarian tribe (they train warrior cats) on a Rocket Ripper. However the hair, cat, and placement of the scratch marks and Dragonmark all match up with an earlier picture of Barbara the Barbarian.

Either theory is plausible.