1. Who's Afraid of Virginia Woolf
Her delivery of the speech describing the birth of her "son" is unparalleled.
2. Cat on a Hot Tin Roof
Cutting edge in the 1950's era of cultural conformity and conservatism.
Also...
3. A Place in the Sun
4. Suddenly Last Summer
5. Butterfield 8
6. Giant
All classics, of course.