Hmmm, I figured it was a trick question and the reason it was five instead of four was because somebody was trying to add in the "Cincy Slam." In that case, I'd go ...
RG: Novak defeats Nadal and gets a career slam, while Nadal gets a career-ending knee injury in the fifth set after nine hours as they try to break Isner-Mahut's Wimbledon record for the longest match.
Wimbledon: Fed defeats Murray, setting the stage for an Olympic medal win on the same surface weeks later, also against Murray — allowing a rare double humiliation of Murray on home soil.
Cinci: Fed defeats Murray. Why not a humiliation in the U.S. just for variety?
U.S. Open: Fed saves two match points to defeat Novak.
Australian Open: Novak pays Fed back with a straight-sets AO defeat.
(If Cinci wasn't intended as the fifth slam, I'll go with Fed beating Novak at the French to get his second career slam, while Rafa falls to Esther Vergeer in a six-hour wheelchair exhibition match.)