Trekathalon TOS:1-28 City on the Edge of Forever

The Magic is in the Hole.

This episode is chock full of Joan Collins, a time Doughnut,* and something that made Harlan Ellison angry!  It also won a Hugo award.

Great acting, but unfortunately, the impact of the episode has been diminished, since time travel perils are now well-trodden ground for sci-fi geeks, bullets ahoy:

• 
  I feel sorry for the poor vaporized bum, guess he had no impact on history whatsoever?
• How does Spock's homebrew computer work?  How does it know the future?
• Did anyone ever check back on the Guardian of the Doughnut of Time?  Even if time travel itself was to dangerous, couldn't they record pictures, or have a nice conversation?

Hit up wikipedia for the behind-the-scenes kerfluffle over the script and Ellison.

*Opera's spell checker has no idea how to spell doughnut, I wonder what they're called in Norway?