Here's an interesting tidbit of trivia about the film "Gladiator" directed by Ridley Scott,

In the film, the emperor and crowd put their thumbs up for "live" and down for "kill." In reality, the emperor would to cover his thumb with his four fingers for "live." The gladiator would also live if the emperor yelled the Latin word for "dismissed," or threw a piece of cloth, showing mercy. When he wanted the gladiator to die, he would put his thumb straight out to the side, symbolizing the sword. Studies of Roman artwork suggest that the "thumbs up" gesture was actually an affirmation to proceed with the kill.

“Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you.”