Since you didn't specify either written or performed, my inclination is to turn to the shorter plays, not merely from the fact that they are shorter, but students are able to remember so much more from a shorter play, and thus experience "more" Shakespeare. The longer the play, the less taken seriously it becomes. Especially with Hamlet, there are now versions called "the essence of Hamlet" and the "essential" Hamlet. I never stop hearing from students "Can you tell us the important parts?" as if Shakespeare wrote "inferior" parts on purpose and some sections d o not matter. With his shorter plays, Shakespeare packs more into them, the action moves along at a rapid pace, and the suspense never dies. And, with witches, magic, sword fights, how can one go wrong?