One of my favorites is the "green-eyed monster" quote -
O, beware, my lord, of jealousy;
It is the green-ey'd monster, which doth mock
The meat it feeds on. That cuckold lives in bliss,
Who, certain of his fate, loves not his wronger:
But O, what damnèd minutes tells he o'er
Who dotes, yet doubts, suspects, yet strongly loves!
I love words and phrases that people use everyday without realizing that they're quoting Shakespeare! :) Another of these:
I pray you, in your letters,
When you shall these unlucky deeds relate,
Speak of me as I am; nothing extenuate,
Nor set down aught in malice. Then must you speak
Of one that lov'd not wisely but too well;
Of one not easily jealous, but being wrought,
Perplex'd in the extreme. . . .