I'm no speedrunner but I did practice SMW Lunar Dragon for a while and decided it would take ages and I didn't have the skills to pull it off.

SummoningSalt is technically not a speedrunner, no? edit: Oh I guess he is.

If we go outside that I would say the movie King of Kong or some of its collaborators. If you look at the timing the games done quick stuff started in Nov. 2007 and King of Kong came out in Jan. 2007.