I haven't read any of the later incarnations of the title, but the original Moon Knight series from Marvel back in the early 80's was awesome. In some ways, MK was Marvel's take on Batman, with one of the Dark Knight's most prominent creators, Denny O'Neil, handling the series' editorial chores – but Moon Knight had some pretty unique character traits of his own.
As well as an incredibly cool costume.
The series featured clever, twisty, noir-influenced mystery scripts by Doug Moench, playing up the character's multiple identities, and literally groundbreaking artwork by a young Bill Sienkiewicz, who evolved from a loose Neal Adams clone into one of the medium's most innovative artists over the course of the first year or so of the series. This cover is from Issue #8, with Sienkiewicz still in his Adams phase, but beginning to exhibit some of the strong graphic design sensse that would later make his reputation.
A great series, and a great cover.