Barbara Gordon's Batgirl costume is one of my favourites, but it's precisely the original one by Carmine Infantino and Sid Greene (accept no substitutes). Sid's use of lots of black on the costume (I wonder what his bill for india ink must have been by the end of the year) that really made the costume for me. That black contrasts sharply with the yellow. Most other artists that have done the costume just made it grey or purple, lessening the effect.