Waters of Mars
Did he just break time? I hope the ultimate out come of Tennant's swan song isn't undoing all of RTD's lore (last great time war and everything that came after it). Reset everything with a clean slate for Moffat. The Doctor is no longer the center of the universe and goes back to being a fun loving care free fugitive. No more last of the Timelords weight of all reality on the Doctor's shoulders.
I didn't think things would change to drastically when they chose Smith looking all emo or goth, but the new logo, new Tardis, and the first pics of Smith on set make me feel like this is going to be far more drastic of a change than from Eccleston to Tennant. Even though I like Moffats episodes best.