My favorite Khan is Space Seed.
Me too. It wasn't a big action episode, but the dialog was smart and crisp, and I liked the Kirk and Khan scenes.
I know conflicts prevented Shatner and Montalban from ever being able to be at a shooting on the same day, but in my opinion, TWOK suffered from Kirk and Khan never meeting face to face. Most of their dialog was also simply Khan threatening Kirk and Kirk tweaking or taunting Khan.