In my American dictionary and in my synonym finder the word ‘guy’ is clear. It means fellow, chap, friend, buddy, even boy or old man. It can be meant to include females and males in a group as in ‘you guys.’ It is also be a first name for a male child. Guy Madison was an actor who played Wild Bill Hickok back when TV was black and white and there was no such thing as a remote.
In short, ‘guy’ is a friendly word indicating familiarity. We like guys. But the word has an entirely different meaning in England.
Guy was a first name in England and back in 1605, before there was even a Wild Bill Hickok, this Guy, surname Fawkes, was arrested for his part in the Gunpowder Plot. He was part of a conspiracy to blow up the House of Lords in the hopes of killing King James 1 and restoring Catholic rule. Months later, November 5th became an Observance commemorating the plot’s failure. In a few decades it became known as Gunpowder Treason Day.
But over time society and culture changes. That day also became a reason for Puritans to voice anti-Catholic sentiments and burning effigies of the pope and other noted Catholics such as dear old Guy Fawkes. As violence increased the observance of November 5th was repealed in 1859. Today it is celebrated by organized events and fireworks.
The name Guy in England has come to mean a grotesque person. Guy Fawkes, was after all, a traitor and terrorist in the eyes of the protestant country. As a side note, he was to be executed, but he jumped from the scaffold and broke his neck, thus cheating the crown of his death. If interested in what England did to traitors after an execution, you can read the gory details here. http://en.wikipedia.org/wiki/Hanged,_drawn_and_quartered
I bring this up as a note to writers. Remember when creating a character to research the name. If the character is an American we think of good old Guy Madison, a nice guy. If the character is English the association is something else entirely. If you want an English character to be a bad guy, name him Guy-though I am not sure the Brits use that as a first name anymore. If an American character is a bad guy name him Benedict. Research is always a good thing.