Dobby's master
The Malfoys
The spell for killing someone
Avada kadavra
"Not me, not Hermione, YOU"
Ron Weasley
The flavor of Bertie Bott's Every Flavor Bean that Dumbledore ate at the end of Philosopher's Stone
Earwax
The name of Hagrid's hippogriff
Buckbeak
The ghost who lurks in the bathroom and has a crush on Harry
Moaning Myrtle
The spell for opening locks
Alohomora
"It takes a great deal of bravery to stand up to our enemies, but just as much to stand up to our friends."
Albus Dumbledore
The magical device Hermione uses to travel back in time
Time-Turner
Professor Lupin's wife
Tonks (Nymphadora)
Neville's boggart
Snape
The spell for causing rapid growth in the targeted object (making it bigger)
Engorgio
"Oh my god, I've killed Harry Potter"
Neville Longbottom
The type of dragon that Harry selected in the First Task of the Triwizard Tournament
Hungarian Horntail
The professor who taught Potions in Half-Blood Prince
Horace Slughorn
The nickname for one of The Marauders, who is a stag Animagus
Prongs
The spell for healing minor injuries (like a broken nose)
Episkey
Hagrid
The relic from Rowena Ravenclaw that Voldemort turns into a horcrux
Diadem (tiara)
The person who fires the canon during the Triwizard Tournament
Mr. Filch
The witch who put love potion in the candy that Ron ate in Goblet of Fire
Romilda Vane
The spell for bringing inanimate objects to life
Piertotum Locomotor
"Because if it's just you alone, you're not as much of a threat."
Luna Lovegood
The type of hair in Draco Malfoy's wand
Unicorn
The person who had Salazar Slytherin's locket after Mandungus Fletcher
Dolores Umbridge