"There's no need to call me "sir" Professor."

 —Harry Potter and the Goblet of Fire

The Patronus Charm (Expecto Patronum) is the most famous and one of the most powerful defensive charms known to wizardkind. It is an immensely complicated and an extremely difficult spell, that evokes a partially-tangible positive energy force known as a Patronus (pl. Patronuses) or spirit guardian. It is the primary protection against Dementors and Lethifolds, against which there are no other defence.

"Raising her wand, she began to walk in a wide circle around Harry and Ron, murmuring incantations as she went. Harry saw little disturbances in the surrounding air: it was as if Hermione had cast a heat haze across their clearing." —Harry Potter and the Deathly Hallows

"The Levitation Charm is one of the first spells learnt by any young witch or wizard. With the charm a witch or wizard can make things fly with the flick of a wand. The charm is an excellent test of your magical skills, wand control and above all, patience." —Miranda Goshawk, Book of Spells

The Stunning Spell (Stupefy), also known as a Stunner or Stupefying Charm is a charm that is used to render a target unconscious or semiconscious, as well as to halt moving objects.