What's my favorite reader interaction?
Uh, any that are positive? I'm not picky. I'm over the moon when they happen. I'm enough of a human (no, really) to enjoy having my ego fed. I sure as hell ain't gonna dictate how that goes down. Well, don't show up at my house uninvited, but beyond that I'm like a Venus flytrap, snatching up whatever little scrap of "it was good" or "liked it" I can get. I am always grateful when a reader takes the time to let me know.
Now, if you want to see me tap my foot and howl with glee like a happy puppy...that'll be from fan art. I haven't received any yet, but I love, love, love seeing what fans draw for other authors/stories/characters. Those skills, man, I salute.