Maniacs who decide to forgo any reasonable level of protective clothing in order to be able to dance in battle and are getting away with it (for a while). There are many iterations of this concept in multiple settings such as the Wood Elves wardancer, the Eldar harlequins and countless bard/monk/rogue based classes but they are all mad.
Battle Dancer is one of the "new" based classes in Dragon Compendium, originally appearing in issue 159. It's a variant charisma based Monk that trades a good fort and will save, and the random monk/martial weapons it gets for full BAB and actually being proficient in all simple weapons. It's a pretty terrible class whose only saving grace is being a one level dip for a charisma based character that wants +1 BAB, Improved Unarmed Strike, and Charisma to AC.
The original Dragon article says the class was inspired by capoeira, a Brazilian martial art invented by escaped African slaves.