Scabbers » Originally Percy's pet rat, but was given to Ron when Percy received Hermes. Scabbers was Ron's pet up til his third year when it was discovered that Scabbers was actually Peter Pettigrew in animagus form. Peter/Scabbers escaped and reunited with You-Know-Who. Scabbers was gray and had a missing toe (because Peter lost a finger).
Errol » The very old family owl. He still manages deliveries even if he does tend to fly unsteady and occasionally into windows.
Hermes » Percy's owl he received from his parents after being made Gryffindor Prefect in his fifth year. In Greek mythology, Hermes was the messenger god.
Pigwidgeon » Ron's tiny brown and very hyperactive owl. Ginny named him but everyone seems to call him "Pig". Ron seems annoyed by him, however, as he did refer to Pig as a "stupid little feathery git". He was given to Ron by Sirius Black after Ron became pet-less due to the "Scabbers" incident (see Scabbers above).
Arnold » Ginny's pet Pygmy Puff which Molly bought for her at Weasleys' Wizard Wheezes before her fifth year. Arnold tends to ride around on Ginny's shoulder which attracts the attention of Crookshanks. Pygmy Puffs are miniature puffskeins with round balls of fluff in shades of pink and purple.