A burning knuckle is an attack found in the Fatal Fury and King of Fighter games, and is generally done by Terry Bogard. He first lifts his arms and yells "Burning Knuckle!" but can miss-interpreted for "BROWNIE" in some games, he then quickly dashes up to the opponent and delivers a hard punch.
Rock Howard, Terry's disciple, has his own rendition called Shining knuckles were he uses his shoulder instead of his fist.
A burning knuckle is great at getting to your opponent quickly, but watch out for low kicks and counters.