For Aldo definitely the double flying knee KO. It's funny this is up because I just saw a rerun of the Aldo/Mendes fight last night. The knee against Mendes was special because it seemingly came out of nowhere, and it finished him with 1 second left in the round. But the double knee KO wins by a mile in my book. I mean they walked out, and that was it. Aldo timed it perfect, connected with both knees and that was it. It was the first strikes thrown in the entire fight. I remember jumping out of my chair when I saw that.
As for KZ. I will admit I am a bit bitter about him beating Poirier, but I still think the twister was more impressive. It is just something you never see whereas a darce isn't as common as other subs, it certainly wasn't the first time I had seen it.