Blasted by Sarah Kane seriously impacted my thoughts about theatre and what its purpose is and how that best can be achieved. I've never looked at a play the same way after having seen that.
Mamet's Oleanna was in the front of my mind for about a week after I read it. That play seriously challenged me.
August: Osage County
The Goat, or Who Is Sylvia?
Death of a Salesman
Tarell Alvin McCraney's The Brothers Size
How I Learned to Drive- Paula Vogel
When it comes to musicals:
The Last Five Years
Follies
Theatre is a safe place to do the unsafe things that need to be done.
-John Patrick Shanley