Continuing to watch the third season...
"Spectre of the Gun"
Basically, "The Corbomite Maneuver" crossed with "Arena." And yet, it's one of my favorite episodes of the series. I love the surreal atmosphere of the incomplete western town, as well as the look of the Melkotian. The closing sequence, which places Spock's mindmeld in counterpoint to the impending doom of the Earps, culminating in the fence being torn to shreds behind Kirk, McCoy, Spock, and Scotty while they are unharmed at the end is simply sublime. Yes, Chekov's resurrection is a clumsy moment, but at least an explanation is provided.
"The Savage Curtain"
A rather silly outing, with a few hints of brilliance. The scene between Uhura and "Lincoln" is a nice moment. The introduction of Colonel Green, Kahless, and Surak nicely expands the Trek universe (though Kirk's complete ignorance of Vulcan history is hard to believe).
Scotty places Lincoln's presidency three centuries ago, and Kirk mentions that they can convert to minutes and miles, even though they regularly use both units of measure. Even this late in the series it's annoying that such details couldn't be cemented down.