Do I even need to introduce this? Okay.... I like TNG more, but that doesn't stop this from being one of the most fun, visually appealing, creative, important, and influential TV shows of all-time. There, now look at my list.
25. 'The Corbomite Maneuver'
Season 1, Episode 10
The first full space battle episode of the series, setting the standard for what to expect from future military strategy episodes (and movies). The ending is another great early example of the kind of themes you can expect from the show, as it makes you reconsider the villain and their motivation.
24. 'The Conscience Of The King'
Season 1, Episode 13
This could have been a top 10 episode for me had it not stumbled its way through the ending, ignoring the potential dissection of self-inflicted punishment and rehabilitation. That being said, this is still an excellent mystery that plays out like a slasher movie in space.
23. 'Dagger Of The Mind'
Season 1, Episode 9
Do you like watching shows about evil doctors that zap their patients with electrics that drive them mad, keep them sedated, and make them only sicker and more violent? Me neither. This episode sucks. It's pretty great.
22. 'The Menagerie, Parts I & II'
Season 1, Episodes 11 & 12
The re-purposed original pilot for the show assembled as a two-parter focused on bulbous telepathic aliens who want to keep human's captive in a sort of space zoo. The first half is a brilliant set-up with Spock risking his life and career, and the way the story pays off is appropriately subdued and thoughtful.
21. 'The Savage Curtain'
Season 3, Episode 22
Not every Star Trek episode needs to be particularly smart and/or thought-provoking, and when it comes to these mindlessly fun episodes this one is really hard to beat. It's a battle royale with a giant blobby alien pitting Kirk, Spock, Abe Lincoln, and a legendary Vulcan named Surak against some of the most evil beings in the universe. It's fantastically silly.
20. 'Where No Man Has Gone Before'
Season 1, Episode 3
The second pilot episode of the show, which features a conundrum Kirk must face as he is given no option but to kill his good friend who has been corrupted by an alien force that's granted him special powers and warped his mind. Not as cerebral as the original pilot, but just as smart and challenging for the characters.
19. 'The Enterprise Incident'
Season 3, Episode 2
A decidedly challenging episode, this one puts the Enterprise crew in the difficult position of being the villains of the episode just by following orders. It's a pretty sleazy episode that makes you feel a little uncomfortable towards the so-called "morals" of Starfleet and the justification for their disreputable actions.
18. 'Shore Leave'
Season 1, Episode 15
When the crew of the Enterprise visit a beautiful planet for their shore leave, they discover strange happenings abound on the planet. It's an imaginative and fun episode that doesn't try to be deep and is all the better for it. It's almost like the show was taking a vacation from itself.
17. 'This Side Of Paradise'
Season 1, Episode 24
Another shore leave episode (of sorts) and one of the few examples in the show of a looser, less emotionally repressed representation of Spock, who falls victim along with the rest of the crew to the narcotic effects of a space spore. It's great to see this side of Spock, and the emotional climax to his part of the story makes this episode.
16. 'Court Martial'
Season 1, Episode 20
Not many episodes in the original series allowed the events of surrounding episodes to have any impact on the stories they told, with the exception of this one. While TNG handled a similar type story to this better in 'The Drumhead', this was still an uncommon step for the original show and one that definitely paid off. Courtroom Star Trek is usually great.
15. 'Let That Be Your Last Battlefield'
Season 3, Episode 15
Star Trek wasn't always the most subtle when it came to social and political commentary, so it really shouldn't come as a surprise that we they handle racism, they were pretty on the nose. But that doesn't make the message any less true, and the end result any less tragic. It's well-handled in spite of its exaggerated nature, and gave us some iconic one-off aliens.
14. 'The Galileo Seven'
Season 1, Episode 16
One of those great, simple episodes that's more about the execution of the story as opposed to the message it's trying to get across. In this one we see what happens when the cool logic of Spock is put in charge of a difficult situation with no clear-cut logical path to victory. It lets Spock develop as well as recognize the occasional necessity of rash decision-making.
13. 'The Doomsday Machine'
Season 2, Episode 6
While TNG was no stranger to rogue Starfleet captains with a need for vengeance, it wasn't exactly common in the original series. The acting here, while suitably over-the-top, is among the most passionate in the entire show. It's a pretty dark episode, and one of the most substantial in terms of sheer scope.
12. 'The Naked Time'
Season 1, Episode 4
In theory, an episode about the members of the crew losing their sense of self-control (especially so early on in the show) should have probably not worked so well, but Star Trek isn't just any show. It made all sorts of unlikely things work out just through sheer charm. This is a strong episode with a good sense of humor and urgency.
11. 'The Enemy Within'
Season 1, Episode 5
My girlfriend's favorite episode of the show, and I genuinely can't blame her for that. First off, evil Shatner is hilarious. Secondly (and perhaps more importantly), the space dog is among one of the greatest images in all of Star Trek. It's hard not to laugh looking at that thing. In the end this is a pretty silly episode, but I like silly sci-fi, and the ideas behind it are actually pretty clever.