I don't think I can chose a favorite, but I really liked this one.
"Horror is looking into the eyes of the Shadowed One, knowing you are about to die...and then being forced to live. Horror is waking each day to see every part of your body moving on its own, a shifting mass of Protodites where once was solid metal and living tissue. Horror is what is in the eyes of your partners when they look at you...and in the cries of your enemies when your swarm engulfs them. Don't talk to me about fear, creature--I am fear!"
—Zaktan standing up to Irnakk, BIONICLE Legends 5: Inferno
I always liked this quote because Zaktan was standing up to literally his worst fear in the chamber of nightmares.