Confundus Charm
Incantation: Confundo
Pronunciation: kon-fun-doh
Description: Causes the victim to become confused, befuddled, overly forgetful and prone to follow simple orders without thinking about them.
Seen: In Prisoner of Azkaban Severus Snape suggests that Harry and Hermione had been Confunded to believe Sirius Black's claim to innocence (Why don't you stop sticking your nose where it doesn't belong, Snape?! You're leaving a trail of grease all over!).
In Goblet of Fire, it is suggested that a powerful Confundus Charm is responsible for the Goblet choosing a fourth Triwizard contestant.
When Hermione uses it on Cormac McLaggen during Quidditch tryouts in Half-Blood Prince. (Haha, sike! )

Conjunctivitus Curse
Incantation: Conjunctivitae
Description: A curse that causes great pain to the victim's eyes.
Seen: Used by Viktor Krum as an ideal method of defeating the dragon. Cast by Madame Maxime against giants.

Cruciatus Curse
Incantation: Crucio
Pronunciation: krew-see-oh
Description: Inflicts unbearable pain on the recipient of the curse. One of the three Unforgivable Curses. Only works if the caster truly desires to inflict pain on the victim.
Seen: Used against Frank and Alice Longbottom until they were pushed to the brink of insanity.
Introduced by Barty Crouch Jr. (acting as Moody) who used it on a spider. Used regularly by the Death Eaters as torture, and by Voldemort as punishment, even against his servants.