Already read the Dexter series, the Kane and Cane series (One's sci fi, other's fantasy, somewhat similar even in names, both were assassins at one time, odd coincidence), American Psycho, and the Artemis Fowl series.
Fantasy and sci fi are prefered but if you know a good novel/series that isn't, I won't mind.

Oh and I've also read the Thomas Covenant series, hitchhikers guide (Barely counts but the president is sort of an antihero), the hannibal Lecter series, and the vampire chronicals, .