*not a huge...

Obviously, there's "Twelve Angry Men" - only slightly more than ten people.

If they're all young (in other words, capable of playing teenagers realistically), I think "Shakespeare's R & J" by Joe Calarco (Dramatists Play Service) is a spectacular show.  It's a condensed presentation of "Romeo and Juliet" with four young men acting all the parts.  The catalogue description reads as follows:

"Four young prep school students, tired of going through the usual drill of conjugating Latin and other tedious school routines, decide to vary their governed lives.  After school, one breaks out a copy of William Shakespeare's "Romeo and Juliet" and they all take turns reading the play aloud.  The Bard's words and the story itself are thrilling to the boys and they become swept away, enmeshed in the emotion so much so that they break school rules in order to continue their readings.  The rigidity of their lives begins to parallel the lives of the characters in the play: roles in the family, roles in society and the roles played by men and women soon seem to make all the sense in the world, and then, suddenly, they seem to make no sense at all.  Although they had been taking turns playing all the parts, two eventually emerge playing Romeo and Juliet exclusively, bringing a whole new dimension to the proceedings.  Perceptions and understandings are turned upside down as the fun of play acting turns serious and the words and the meanings begin to hit home and universal truths emerge."

This is a great show.  I highly recommend it.