TOS-r: A Taste of Armageddon
"Archons" and this are my two favorite planet stories. Both establish templates for the many planet stories to follow which turn events in both these episodes into overused cliches. Latecomers to Trek are often unable to appreciate these two shows because they don't realize that they were the first of their types.
"Armageddon" is an exciting action adventure filmed entirely on the soundstage with no location work. It keeps the viewer entertained, while wrapping everything in a good anti-war message.
Shatner looks incredibly trim and fit here, with several action moments, including a well choreographed fight against two stuntmen, doing it all himself with no double.
James Doohan gets some of his best scenes in the series, going nose to nose against Ambassador Fox, especially when he flatly refuses to follow given orders.
And Miko Mayama has her own tough woman moments as Yeoman Tamura. It's too bad they never brought her back trapped with Sulu in a danger situation, those two planning an escape could be something.