The word Goon is a relatively new term that has recently spread from an arena generally only used by rappers and those in the African-American culture, to all races and ethnic areas.
In a pop culture sense, "goon," has been used in many popular songs by artists who are quite famous.
Rapper Brisco, among others, uses the term to describe himself and his friends from a particular region of Miami in his song featuring Lil' Wayne "I'm in tha Hood": "Opa-Locka Goons!"
Thus we see the definition of "goon" being applied in a geographic sense, identifying a group of people from a certain region with a set of shared characteristics or habits.
"Goon," primarily through the lyrics of rapper Plies, has begun to take on a similar, but new meaning to Brisco's usage. Plies is a rapper notorious for being the tough guy on the block, the "G" who has never snitched, and is going home to his "Bust it Baby" in one piece or in a casket. Plies persistent use of the word to describe his large group of thugs has caught on in a humorous sense with rap-listeners and non-listeners alike.
With the advent of the word being used in a such a serious manner, it has grown to describe a variety of people and individual characteristics.
A goon can be a thug - someone who you know at any given time could rob a conveinence store for you.
Ex: "That kid's a goon - I wouldn't mess with his girl bro."
A goon can be someone who acts goofy, strange, or simply humorously during inappropriate times.
Ex: "We brought over a girl for him to spit game at - but he was a goon and played beer pong all night instead."
A goon can also be someone or something that is mischievous, clever, or crafty.
"I've got a date on Wednesday, Thursday, and Friday; the girls are all friends, but none of them know...I'm a goon if I pull it off."
A situation where many goons are present in a contained space, or an event run by many goons, would be referred to as "goonville," or "Goon Squad."
Ex: "Look at this "goon squad," let's get outta here.
The step above a goon (which of course is all relative to how much of a goon "person A" is) would be a "Goblin."
It's going down tonight, cuz them goons out lurkin'
All the goons around me so you know I'm comin'
Half a brick in my pocket ten stacks on me!