All of these gimmicks of Mick Foley's were great. With Mankind, Foley took the character in several different directions: demented, tortured maniac who played with pet rats and infamously called Goldust "mommy." Then, he molded the character into corporate America by giving him the shirt and tie, a tie back to his attempts to be the favorite of Vince McMahon. From there, and after the summer of 1998, he tried to make the character more kid-friendly and more comical, essentially making Mankind more of an extension of Foley's personality.
Cactus Jack was the straight up hardcore gimmick, a character that would maim himself to take out his opponent. He didn't mind taking dives onto concrete or jumping through tables. If it hurt his opponent, so be it. Other than the run in ECW where Jack went anti-Hardcore, Cactus was the wildest of Foley's personalities throughout his career. It was remembered fondly enough to where the character was brought into WWF with much success. If Mankind was the demented, sick version of Foley, then Cactus was Foley's psychotic, sadomasochistic version that was used to elevate a feud. Take this for example:
http://www.youtube.com/watch?v=68gwIbZ6jQ8 .
However, I have to admit, my favorite gimmick of Mick Foley has always been Dude Love. There was such a good build to the emergence of the character on TV. There was the interview where Foley talked to J.R. about being Dude Love in a video. Then, there were subtle hints on TV that Dude was going to appear until finally, when Steve Austin needed a tag team partner to fight off Owen and Bulldog, Dude Love made his WWF debut:
http://www.youtube.com/watch?v=-bQsqSyCaUs (8:00 in). Dude Love was Mick Foley at his most ridiculous comically. When Foley brought Dude back in 1998, Corporate Dude Love was the perfect villain for Steve Austin to go against. Someone Austin had tag teamed with in the past and the antithesis of everything Stone Cold Steve Austin was: colorful, comical, light-hearted, and a corporate sellout. Foley played the part to a T.
Dude Love was my favorite gimmick of the "Three Faces of Foley."