I recently watched this underground gem that really isn't all that old. "The Man from Earth" is a superb movie whose setting takes place in one room. I recommend it to everyone here on volconvo as it is remarkably relative to most conversations had on here.
Here's the synopsis:
A professor gathers his academic friends/colleagues and confesses that he is a caveman who has been alive since prehistoric times thanks to a gene mutation allowing his cells to replicate without error. This claim is of course met with much skepticism, resulting in some very intriguing conversation about mortality and the history of mankind.
It scored a 7.9 out of 10 on IMDB and an 85% on Rotten Tomatoes.