Yesteryear The Slaver Weapon Beyond the Farthest Star One of our Planets is Missing The Eye of the Beholder
TAS top five episodes for myself: Time Trap Slaver Weapon One of Our Planets is Missing More Troubles, More Tribbles Ambergris Element
The fun thing about the animated eps is that the novelizations came out not long after. They do very well to flesh out some of the stories into some really solid Sci-Fi.