What are some of the most famous Shakespeare quotes?

In Act II, Scene VII of As You Like It, the hopelessly melancholy character, Jacques, says that

All the world's a stage,And all the men and women merely players. They have their exits and their entrances, And one man in his time plays many parts, His acts being seven ages.

In comparing the world to a stage, men and women to actors, and life to a play, Jacques makes life seem less meaningful than we typically think of it as being. He says that in the first act, we play a baby, crying and spitting up in our nurse's arms; next, we are whiny schoolchildren, unwilling to go to school; third, we become lovers, writing sad poetry; fourth, we are soldiers, eager to fight; in the fifth act, we become judges, respectably bearded with bellies fattened by bribes; sixth, we become skinny and old, wearing ill-fitting clothes and speaking childishly; finally, we enter a second childhood, lacking teeth, sight, taste, and everything else. It is implied that there is little to no deviation from this pattern, and our sad second childhood is inevitable and dreadful.
In Act V, Scene V of Macbeth, the titular character speaks in a very famous soliloquy, saying that life

is a taleTold by an idiot, full of sound and fury,Signifying nothing.

For him, at this point in the play, life has no real meaning. It seems to him that we live believing that our lives are full of emotion and importance, but we eventually realize that life is only a rambling story that seems really exciting and full of important things but that is ultimately meaningless.