My favorites are:
Three Tall Women (Albee)
hamletmachine (Muller)
A Streetcar Named Desire (Williams)
Topdog/underdog (Parks)
The Intelligent Homosexual's Guide... (Kushner)
The Homecoming (Pinter)
Any Brecht
Any Caryl Churchill (especially Cloud Nine)
The Chairs (Ionesco)
And failsafe, I agree with you 100% about Other Desert Cities. I saw it on Bway and, while the cast was superb, I found the play to be lazy, obvious, and safe.