#1 Worst: The New Day win the SmackDown tag team titles
The New Day would have become instant heels had they won the titles in front of a live audience, I feel. And this is not because they lack talent, because we all know that they do not, but they have had far too many runs with the belt and the audience has really grown tired of them.
Because they have been one of WWE's most popular acts in the current era, there has been no change in their gimmick over the last few years and that is why many have been saying that their whole shtick has grown stale with the passage of time in WWE. As creative as they are, sometimes you need to be like Chris Jericho, changing up your gimmick to a major degree to stay fresh and relevant in the business, for your fans.
Also, The Miz and John Morrison have been great and I don't think they should have lost the titles yet considering they had a lot more to give!