I love this film and others of the same type -that is, movies that could easily work as plays as well. Do you know of any others? My personal recommendations are:
Exam
The Rope
12 Angry Men
... and of course, my favorite: The Man from Earth
What about Sunset Limited? (it's about a very different issue by the way).
shareGlengarry Glen Ross.
shareSome great suggestions here including my favourite...
The man from earth
The sunset limited is very very good as well
The exam is also another worthy mention although a different style
A fantastic addition is My dinner with andre
Another not quite so good is chinese coffee.
I love this genre so anymore suggestions are very welcome