I found this in another newsgroup. :-)
A man walks into a bar and says to the bartender, "Beer for me, beer for you, and beer for everyone who is in the bar now." After drinking, the man starts walking out of the bar. "Hey, what about the payment?" yells the bartender. "I have no money," answers the man. The bartender hears that and beats the man as hard as he can, then throws him out into the street.
The next evening the man walks again into the bar and says to the bartender, "Beer for me, beer for you, and beer for everyone who is in the bar now." The bartender thinks to himself, "The man can't be stupid enough to pull the same trick twice, tonight he must have enough money", and gives beer to everyone. After drinking, the man starts walking out of the bar. "Hey, what about the payment?" yells the bartender. "I have no money," answers the man. The bartender hears that and beats the man as hard as he can, then throws him out into the street.
One evening later the man walks again into the bar and says to the bartender, "Beer for me, and beer for everyone who is now in the bar." In disgust, the bartender asks "What, no beer for me this time?" "No," answers the man, "you get violent when you drink."