I can't vouch for the current printing, but my friends and I had a very active, and enjoyable campaign in high school. The game is called Pendragon and was originally published by Chaosium. It's changed hands a couple of times and is now published by the Arthaus imprint of White Wolf.
http://www.white-wolf.com/pendragon/Unlike a lot of RPGs, this one has a lot of room and incentive for roleplaying chivalric ideals, behaviors, etc. And if you're a good boy, you might just become a Knight of the Round Table...
