When you want someone to make a fool of themselves by reenacting something they just did or said. If they're gullible they will do it over and over. Works best on blondes.
Megan: That girl over there was like *Does stupid face*
Michael: Like What?
When someone just looks so moronic and idiotic, you just have to call them a goofy fuck.
Matthew: See that dude over there with the big square head?
Cody: Oh David? Yeah, he's a Goofy Fuck.
When someone is so badass is does something epic, they are a fuckin guy.
*Cody does a front flip over a friend*
Michael: Dude did you see that?
Matthew: Yeah, He's a fuckin guy!