At university, we had an exam for the Shakespeare course; we had to know about a hundred quotes by heart for the written part, and his biography and interpretation of his works for the oral part of the exam. You just reminded me about that. The first one that comes into my mind is:
''There is something rotten in the state of Denmark.'' (Hamlet)
I actually say this one out loud when I ''smell'' that sth is wrong.
or, another famous one:
''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.'' (As you like it)