An expression of hate or derision. Popular at MIT in the early 2000s, from which it spread to the internet at large. Possibly a reference to Full Metal Jacket, in which the drill instructor threatens to "gouge out your eyes and skull-fuck" a recruit.
And, "for fuck's sake" = "for the sake of fuck". Just as "for Pete's sake" = "for the sake of Pete", or "for goodness' sake" = "for the sake of goodness".