I threw and attended a whole slew of great parties this year, but my highlight party was for my birthday last summer. It didn't involve every person I might have wished could be there, and it wasn't a huge party that reached deep into my social circle to include every last person whose company I enjoy, and it wasn't the surprise party I sometimes fantasize about having, but it was, nonetheless, a highlight evening of my year.
It was basically a perfect party for me: everyone had a good time, there was no drama, all sorts of different kinds of fun were had, people wound up sitting on the kitchen floor for intense conversations, there was music, and dancing, and tasty treats. Thinking about it months later still makes me smile.