A person or thing that is the direct opposite of someone or something else.
Example: In Romeo and Juliet
-Love vs Hate
-Fate vs Freewill
-Loyalty vs Disloyalty

understatement, especially that in which an affirmative is expressed by the negative of its contrary
Example: This is going to ruin my whole day (after getting shot in Avatar)

A play on words.
Example: In the Great Gatsby
"Ask for me tomorrow, and you shall find me a grave man...."

A rhetorical device in which two seemingly contradictory words are used together for effect.
Example: In the Great Gatsby
-"I was a pathfinder, an original settler."
-"This is a valley of ashes."

a self-contradictory and false proposition
Example: In the Great Gatsby
-Nick wanted to 'look squarely at everyone, and yet to avoid all eyes'

A synecdoche is a figure of speech in which a term for a part of something refers to the whole of something, or vice-versa.
Example: "I became a transparent eyeball I am nothing; I see all; the currents of the universe being circulated through me"