re: What are your 5 favorite Star Trek: The Original Series episodes?

For different reasons, those are fun episodes -

A Piece of the Action was about as campy as Trek got. Space Hippies (The Way to Eden) was the bad kind of campy, inadvertent. But they clearly went all in for A Piece of the Action, the regulars, the guest stars, the extras, the writers, the director - the fact they all enjoyed making that episode is obvious in the final product.

The Enterprise Incident, really only the second significant treatment of Romulans, was groundbreaking for Trek. Spock only got a couple of romantic leads (despite Nimoy's fan mail from female fans dwarfing all others, combined, including Koenig) and that, combined with a faux heel turn (and not under the influence as before) and the Romulan culture (female commander ) combined to make this an intriguing, entertaining episode.