I'm not sure if this one counts really, but Tom Watson winning the 2009 Open Championship over Stewart Cink. Watson was 59 years old - easily would've gone down as one of the best majors ever (it's still a really good one, even if Cink didn't do anything after that win).

Give Tom Watson the 2009 Open Championship. If you want to follow the rules above, have him beat Cink in the 4-hole playoff.