William Shakespeare's works are rich with lines that have become iconic over the centuries. 

Hamlet

"To be, or not to be: that is the question."

As You Like It

"All the world's a stage, and all the men and women merely players."

Julius Caesar

"Cowards die many times before their deaths; The valiant never taste of death but once."

Romeo and Juliet

"What's in a name? That which we call a rose by any other word would smell as sweet."

Othello

"O, beware, my lord, of jealousy; It is the green-eyed monster which doth mock the meat it feeds on."

Twelfth Night

"Be not afraid of greatness. Some are born great, some achieve greatness, and others have greatness thrust upon them."

The Merchant of Venice

"All that glisters is not gold." 

Sonnet 18

"Shall I compare thee to a summer's day? Thou art more lovely and more temperate."

Henry VIII

"Heat not a furnace for your foe so hot that it do singe yourself."