As far as shock and surprise, I voted for:
10th gen announcement - Definitely a shock with how soon it came about, and unfortunately it means it's still gonna take me a while to warm up to the winners and the drastically new look of the group. But as long as 9th gen remains awesome and their awesomeness rubs off on 10th gen through increased interactions I think I have a lot to look forward to.
Yuuka graduating - The S/mileage audition and Saki's graduation make sense when looked at together, but I thought that would be it. The signs were there (Yuuka looking less-than-enthusiastic, all the submembers getting promoted) but I was simply caught off guard.
Aibon's attempted suicide and
pregnancy/marriage - It speaks a lot on how sad and rough her life has been that some people are not shocked by this, but personally I thought she had shed those dark times behind her with her post-H!P comeback. Getting hitched and knocked up...well, I'm still blown away by that.
The return of Asuka Fukuda - I don't think there was any way anyone could've predicted this. I'd been convinced she was done with showbiz completely.
Still, I think several other news items deserve recognition for memorability. 9th gen results were everything I could've asked for and more. Ai-chan's graduation was at the very least kind of a big deal considering her tenure.
Yuko finally getting her man is something we all wanted but never really knew when or if it would ever happen. I think Mari's marriage deserves some mention, because LOL at that height difference.
And there seems to be some drama going on with Tsuji's marriage but that story's only now starting to unfold and will be something to look out for in the new year.
I've never actually watched a full episode of Tsuntsube but judging by shi's reaction I'm starting to understand why each video I glance at has so many dislikes.