The most common complaints my English teacher friends hear when they start a new unit on Shakespeare in their classes is that their students don't understand the words he used in his plays. And it's true, a lot of the words--for better or worse--are no longer used. (Seriously, how did ZOUNDS go out of favor? It's a most excellent word.)
The thing is, though, that for every archaic and discarded word you'll find in Shakespeare, you'll find hundreds more that Shakespeare invented, words that are still used today.
Words like--accused, bandit, bedroom, blushing. According to Shakespeare online, the bard invented 700 modern words (ode, Olympian, grovel, tranquil, thoughtless). If you like words, check out their page on the subject here.