Some TV eps:
Aquiel: The revelation of the blobby critter, as exemplified by the hand that pokes up out of the container Crusher was examining.
Unification II: The discussion between Spock and Picard is a standout scene, even if the rest of the episode is a mess.
The Empath: The most superficial and padded-loaded storyline, there's this jaw-dropping gem of a scene:
Only Spock would call McCoy's decision, of all things, "unethical". And the clip ends with Gem shedding a tear. It just about makes up for everything preceding it.
The Omega Glory: Morgan Woodard command in this episode, and the story's opening - which suggests a nice mystery/suspense plot - is finding the reason for why a crew of people on a starship all died horrible deaths and turned into big alum crystal piles (and how the Enterprise crew also have the malady and need to find a cure.)
Descent II: The concluding episode may be a shark jumper, but it still had this fun little camptacular moment:
(Note that Lore is pumping Data's favorite anti-drug at just the right time, since sober Data would never feel delight at anticipation of his best friend about to be murdered and stuff.)
Spock's Brain: The show got budget cuts, but they sure did spend on a nice backlit projection screen and some terrific use of it in the episode that actually felt refreshing and new, especially for the premiere of the ill-fated third season. And, of course, the ol' standby of "BRAIN AND BRAIN! WHAT IS BRAIN!!!" Actually, Marj Dusay is another actor in a select handful therein, of actors who took an iffy role and put in a really good performance.
Pretty solid acting considering how much cringe the story was back then... Am amazed that youtube doesn't have fifty remixes of that phrase yet... I recall a later scene where she gets to turn all evil and wield a phaser. Couldn't find a youtube, but some Trek episodes allow an actor to show some range and she had range that ranks up there with Shatner's and plenty of Trek episodes show him being subtle and very much on the mark as well...
Code of Honor: More or less a bunch of scenes: Jessie Lawrence Ferguson, who easily commands every scene he's in, is the perfect actor to complement Patrick Stewart. Both are fantastic actors. In this story, both have incredibly bad dialogue. Dialogue so bad that it made that day at the zoo where all the elephants had simultaneous and massive tummy troubles seem more less stressful to observe by comparison. And yet, here they are, both actors, both elevating dialogue to something that's surprisingly watchable and far better than the episode deserved to be, though in fairness the episode
is chock full of half-baked, corn-filled scenes. Indeed, Picard wants Geordi to focus on the weapons' sharp edges, instead of Data who - you know - can't be killed by the weapons and what might be laced on them, as a later scene is quick to reveal for uberscary dramatic effect... sigh... The points others said are points I'd second as well; the fight scene is solid and the Geordi/Data seen should not be missed as it's also a highlight.
Turnabout Intruder: I've said it before and will happily say it again. Any scene with Sandra Smith and William Shatner prop this podgehodge of a story up more than it deserves to be, because both excel and really sell the concept of minds transferred into other bodies. Even better, they don't go over the top or act it amateurishly as much as other shows and casts might do with similar material. (Red Dward's episode "Bodyswap" is another example of mind swapping done extremely well.)
Threshold: Apart from SF Debris' review, the episode also gave us... well, this review and I can't get enough of this channel: