I refuse to say this is THE best Best Show, because the show's trajectory clearly states that the best is yet to come. I just have to call out the August 31-September 6, 2005 move to Sirius story arc, as those were the shows that cemented me as a Best Show fan 4 life.
Never before or since have I seen a 'prank' (for lack of a better word that doesn't devalue the high art this was) pulled off with such grand design. Over the course of the weeks leading up to his 'departure', Tom plays the entire audience like an award winning fiddle player. He both uses the time to say goodbye, pulling deep emotions from people while showing everyone exactly what they would be missing if he really did leave by putting on some of the best shows in the archive. When it all pays off in one final blow-out love fest you think the worst has passed, the show is gone, but the very next week Tom 'crawls back', torturing anyone who cares with his deep inner pain and showing them the death of his soul. Even when the reveal comes, it still feels like things could go south like that at any minute. That feeling has threaded it's way through every single show and I just love it! It is truly a thing of beauty.