I'll bet anything it was Butch that keyed Vincents car. If you remember the bar scene in Pulp Fiction where Vega is eyeing up Butch calling him Palooka and Punchy, Butch is giving Mr. Vega the "im gonna whip your ass" look but doesnt when the realization comes that Vega and Wallace are good friends. So what does Butch do? After he buys his pack of Red Apples he goes outside and keys Vince's Malibu. So how does Butch know that the red Malibu is Vincents? My guess is that there are no cars parked outside the alleyway entrance to the bar and since there were only Wallace, Paul the bartender, Jules, Vincent , and himself in the bar, plus the fact that Jules and Vince were not in the bar wher the meeting of the boxing match began, Butch assumes the car has to belong to one of the two men who just walked in, since Marsellus Wallace appears to be the type of man who is either chauffered around or has a much nicer ride. Am I right? or do I seriously need to get a life?