Any 5 will do for the most part. Nitrox, Fish ID, Boat diver, Altitude, and UW Photographer will get you a master diver card. And some of the so-called "distinctive" ones like whaleshark, manatee, and hydrooptix mask user qualify as well if memory serves. Along with AOW and rescue. So someone with one deep dive to 61 feet, one night dive, and one navigation dive from the AOW course can qualify as a "Master Diver" as long as they also have 50 dives. According to the instructor manual I have.
You have to have AOW, Rescue, plus any 5 specialties as well as 50 dives.
I don't know what Jim means by "one deep dive to 61 feet, one night dive, and one navigation dive from the AOW course...." Those used to be part of the requirements for AOW. (Night diver was dropped quite some time ago because there are many places in the world where it is very hard--close to impossible--to do a night dive.) I am not sure what he means by mentioning them. They are single dives that one can do for AOW--they are not specialties that count toward MSD. One has to do much more to get the specialties in those areas.