Pendragon

Pendragon is a game by Greg Stafford, of Glorantha fame, focusing on the adventures and romances of the Arthurian mythos in an imagined post-Roman Britain.

It's also one of the worst organized systems I've ever laid eyes on.

What's Good
Stafford does a decent job of accommodating a lot of disparate interpretations of the Arthurian mythos in his system, from the French romances to Welsh poems and even the anachronisms of T.H. White's Once and Future King. The Great Pendragon Campaign has a hell of a lot of resources for a GM to help bring his game some backdrop for the players to work in.

What's Bad
The core books are alright, even if there are some useless skills. It's the splatbooks that add madness and terror to the game. Contradictory costs for the same option, different rules for the same thing in different books, shit more unbalanaced than homebrew games. It's enough to make a GM tear his neckbeard out.