Gosh, it's probably because I'm so old :p but I can't think of a specific moment this year as a favorite. In my teenage years, of course, there were obvious highs and lows (and the drama that came with it!) but I try to keep myself on a pretty even keel now, which means that the happy and the melancholy sort of mix together. I can say that I've founded some new friendships this year, which I hope will continue despite upcoming changes in my life, but of course the work of friendship is the work of many days, months and years... not something that can be whittled down into an afternoon.
In the occasional news I have read, I've sought out the stories showing the positive that people are accomplishing, and I actively avoid the rabbit-hole of fear and dread that passes for currency in many places. I can't recall specifics, but suffice it to say I've read a few long-form articles (one or two from Time, I do believe, but also from other sources) which chronicle the little-observed but hard-fought battles by a person or two who chose to do the right thing, even though it wasn't easy. Even if I hadn't read those stories, I find a lot of hope in my every-day encounters with most people.
The year-end holidays are definitely a time for my to take stock of my own life, which I do privately, but when I consider the whole of our fast-changing society and the petty dramas playing out on this tiny planet, I almost always come back to the words of the wise man who wrote, "What has been will be again, what has been done will be done again; there is nothing new under the sun." As so it goes, for bad and for good. :)