Best friend.

A man was feeling very depressed and walked into a bar and ordered a triple scotch. As the bartender poured him the drink he remarked, "That's quite a heavy drink. What's wrong?"
After quickly downing his drink, the man replied "I got home and found my wife in bed with my best friend."
"Wow" exclaimed the bartender, as he poured the man a second triple, "No wonder you needed a stiff drink. The second triple is on the house."
As the man downed his second triple scotch, the bartender asked him "What did you do?"
"I walked over to my wife" the man replied, "looked her straight in the eye and told her that we were through and to pack her stuff and to get the hell out."
"That makes sense" said the bartender, "but what about your best friend?"
The man replied, "I walked over to him, looked him right in the eye and said 'bad dog!'"