Buford "Mad Dog" Tannen: You owe me money, blacksmith.
Doc: How do ya figure?
Buford "Mad Dog" Tannen: My horse threw a shoe. And seein' as you was the one that done the shoein', I say that makes you responsible.
Doc: Well, since you never paid me for the job, I say that makes us even!
Buford "Mad Dog" Tannen: Wrong! See I was *on* my horse when it threw the shoe and I got throwed *off*! And *that* caused me to bust a perfectly good bottle of fine Kentucky red-eye. So, the way I figure it, blacksmith, you owe me five dollars for the whiskey and $75 for the horse.
Marty McFly: [hoarsely] That's the $80.
Doc: Look! If your horse threw a shoe, bring him back and I'll reshoe him!
Buford "Mad Dog" Tannen: I done shot that horse!
Doc: Well, that's your problem, Tannen!
Buford "Mad Dog" Tannen: Wrong! That's yours. So, from now on, you better be lookin' behind you when you walk. 'Cause one day you're gonna get a bullet in your back.
[Buford and his gang gallop away on their horses]