This term, coined by the legendary Jim Crow of the LNHN, expresses a major victory in getting girl by your unparalleled "mac daddy" nature.
It was originally derived from "tactical nuke", a 25 kill streak award in Call of Duty: Modern Warfare 2 that kills everything and assures complete victory.
Thus, when you call in a "mac-tical nuke", you get that girl to want your dick.
Jane: Hey Joe, what's up!
Joe: Not much bitch, what are you doing tonight? Wanna suck my dick?
Jane: Sure, I'd love to!
Joe (to friend): Mike, I just called in a mac-tical nuke on some dumb bitch!
Mike: Very nice, I get some assist points for that though.