Dragon
This is quite obviously the best of all the creatures. My one true love.

Examples include Smaug (The Hobbit), Tintaglia (The Liveship Traders) and Spyro (Spyro video games).

Mermaid
Mermaids in stories are either super cute or super scary. They're popular in YA at the moment.

Examples include Ariel (The Little Mermaid), Sh'eenaz (The Witcher).

Siren
Sirens are not the same as mermaids. They are totally badass and lure men to their deaths.

Sirens don't usually get names.... sad face.

Pegasus
Better than a horse.

I think these appear in Greek mythology?