"For the Mega-Win," this acronym is a variant of ftw.
Apparently, it also means "Fourier Transform Microwave" to some people.
For the motherfucking win.
Person 1: Did you see Push?
Person 2: Hell yeah! Dakota Fanning ftmw!
Person 1: Ftmw?
Person 2: DAKOTA FANNING FOR THE MOTHERFUCKING WINNNNNNNNNNNNNNN! *cums*