One of the only grammatical instances where the word "fuck" cannot be used. "Fuck" can serve as an adjective (your fuckin' stupid), verb (I want to fuck you), or a noun (you are one miserable fuck). However, when used as a noun, "fuck" is not plural by itself, like the words 'shit' or 'moose'. Fuck can only be plural when an 's' is attached (fucks). People still use it incorrectly though, showing there complete idiocy when they cannot correctly use the most versital word in the English language.
Correct: "You guys are dumb fucks."
Incorrect: "You guys are dumb as fuck."