1. The pets
Buckbeak was Hagrid's beloved pet. He was a Hippogriff who was annoyed and angry at Draco Malfoy, who in Harry Potter and the Prisoner of Azkaban provoked Buckbeak, who then attacked him. Buckbeak was sentenced to death but was never actually decapitated. Harry and Hermione went back in time with the "Time-turner" which saved the Hippogriff from execution. Later on in the film he then comes into the possession of Sirius Black who cares for then there-after. However after Sirius died Buckbeak became Harry's who then gave him back to his real owner Hagrid. Buckbeak was a very caring Hippogriff who was loyal to Harry and all his other masters.
Fluffy was also a pet of Hagrid's. Fluffy was a three-headed dog who lived on the 3rd floor in Hogwarts. He was put there to guard the Philosopher's stone but had a weakness that Hagrid accidently let Voldemort discover. Fluffy would fall asleep to a piece of music. Unlike Buckbeak, Fluffy was very vicious which he had to be to make sure the stone was well protected. This is the reason that the third floor was forbidden to all students who did not wish to die a very painful death.
Peter Pettigrew (Scabbers)
Scabbers or Peter Pettigrew was a pet of Mr and Mrs Weasley's children. He was passed through each child but never made it to the youngest child Ginny. This is because Scabbers true identity had been discovered, by none other than Remus Lupin and Sirius Black who had been blamed and put into Azkaban for murdering Peter and 12 other muggles (non-magic folk). After his true identity was discovered Peter knew that he would have to go into hiding, which he only managed to do because of Remus Lupin having to turn into his other form of a werewolf because of the full moon. Otherwise Peter would've been locked up and eventually killed in the Wizarding prison. Peter Pettigrew attended Hogwarts School